UC-NRLF 


B    M    131    553 

|£  RIO  LOGY 

FOR 

NURSES 


HARRY  W.  CAREY,  M.D.. 


PBOPEBTY  OF  SAN  FRANCISCO  HOSPITAL 


UNIVERSITY  OF  CALIFORNIA 

SAN  FRANCISCO 

LIBRARY 


AN  INTEODUOTION 


TO 


BACTEKIOLOGY 


FOE  NTJESES 


BY 


HARRY  W.  CAREY,  A.B.,  M.D. 

Former  Assistant  Bacteriologist,  Bender  Hygienic  Laboratory,  Albany,  N.  Y. 

Associate  in  Medicine,  Samaritan  Hospital,  and  City  Bacteriologrist, 

Troy.  N.  Y. 


PHILADELPHIA 

F.  A.  DAVIS  COMPANY,  PUBLISHERS 
ENGLISH  DEPOT 

STANLEY  PHILLIPS,  London 
1915 


\°((S 


COPYRIGHT.   1915 

BY 
F.  A.   DAVIS  COMPANY 

Copyright,  Great  Britain.      All  Rights  Reserved. 


Philadelphia,  Pa.,  U.  S.  A. 

Press  of  F.  A.  Davis  Company 

1914-16  Cherry  Street 


PREFACE. 


MANY  of  the  duties  of  the  nurse  require  a  knowl- 
edge of  the  principles  of  bacteriology  in  order  to  be 
performed  intelligently.  It  is  difficult,  however,  for 
anyone  instructing  nurses,  to  decide  just  how  much  of 
the  subject  to  attempt  to  teach. 

The  basis  of  this  book  is  the  lecture  notes  that  I 
have  used  during  the  last  eight  years  in  teaching  the 
nurses  of  the  Samaritan  Hospital  Training  School. 
In  incorporating  them  into1  book  form  I  have  en- 
deavored to  present  clearly  and  in  simple  language 
that  portion  of  the  subject  essential  for  the  nurse  to 
know.  A  few  blank  pages  have  been  inserted  at  the 
end  of  each  chapter  for  the  convenience  of  the  student 
in  adding  useful  notes  from  time  to  time. 

H.  W.  CAREY,  M.D. 


TROY,  N.  Y. 


(Hi) 


CONTENTS. 


CHAPTER  PAGE 

I.    THE  HISTORY  OF  BACTERIOLOGY 1 

II.    THE  CLASSIFICATION,  MORPHOLOGY,  BIOLOGY,  AND  DIS- 
TRIBUTION OF  BACTERIA 6 

III.  THE   DESTRUCTION   OF   BACTERIA,   STERILIZATION   AND 

DISINFECTION  17 

IV.  INFECTION  AND  IMMUNITY 29 

V.    THE  GROUP  OF  PYOGENIC  Cocci  42 

VI.    THE    BACILLI   OF   THE    COLON,    TYPHOID,    DYSENTERY 

GROUP 55 

VII.    BACTERIA  CAUSING  ACUTE  INFECTIONS 70 

VIII.    BACTERIA  CAUSING  CHRONIC  INFECTIONS 91 

IX.    THE  DISEASES  CAUSED  BY  THE  MOLDS,  YEASTS,  AND 

HIGHER  BACTERIA  99 

X.    THE  BACTERIA  IN  WATER  AND  MILK  105 

XI.    DISEASES  CAUSED  BY  PROTOZOA Ill 

XII.    DISEASES  CAUSED  BY  UNKNOWN  MICRO-ORGANISMS  . . .  122 
XIII.     THE  TECHNIQUE  OF  PREPARATIONS  FOR  AND  THE  COL- 
LECTION  OF   MATERIAL   FOR   BACTERIOLOGICAL  EX- 
AMINATION      130 

GLOSSARY 135 

INDEX  140 

(v) 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

1. — Different  forms  of  bacteria 7 

2. — Arnold's  steam  sterilizer 19 

3. — Autoclave 21 

4. — Gonorrheal  pus,  showing  gonococci  within  a  leucocyte  . .     45 
5. — Diplococcus  pneumonise  in  the  heart's  blood  of  a  rabbit  .     49 

6. — Typhoid  bacilli  showing  flagella 57 

7. — Stages  of  the  Widal  reaction  63 

8. — Tetanus  bacilli.     Spore-bearing  rods  from  an  agar  cul- 
ture      71 

9. — Anthrax  bacilli.     Spore   formation  and  spore  germina- 
tion       79 

10.— Bacillus  diphtherias 87 

11. — Organisms  of  Vincent's  angina,  showing  spirillum  and 

fusiform  bacillus 89 

12. — Actinomyces  hominis  (lung)   100 

13. — Microsporon  furfur 102 

14. — Trichophyton  tonsurans  103 

15. — Ameba  coli.    From  dysenteric  stool 113 

16. — Treponema  pallidum  in  smear  from  secretion  of  a  fresh, 

hard  chancre 115 

17. — Plasmodium  vivax,  parasite  of  tertian  fever 119 


(vii) 


CHAPTER  I. 

THE  HISTORY  OF  BACTERIOLOGY. 

THE  history  of  this  science  is  interesting  because 
it  tells  how  the  study  of  bacteria  developed  from  mere 
theories  into  a  science  based  upon  facts.  Long  before 
anything  was  known  of  the  existence  of  germs,  ref- 
erences could  be  found  in  the  writings  o>f  the  ancient 
Greeks  discussing  the  possibility  of  disease  passing 
from  one  person  to  another.  The  agent  of  infection 
was  supposed  to  originate  from  the  air  or  moisture. 

With  the  instruments  of  ancient  times  it  was  im- 
possible  to  see  the  minute  living  particles  which  we 
now  know  as  germs;  in  fact,  it  is  doubtful  that  such 
minute  forms  were  thought  of.  The  seventeenth 
century,  however,  marked  a  new  era  in  the  making 
of  optical  instruments,  Anthony  von  Leeuwenhoeck 
in  1675,  a  linen  draper  of  Amsterdam  in  Holland, 
succeeded  in  perfecting  a  lens  of  much  greater  mag- 
nifying power  than  those  hitherto  in  use.  By  means 
of  this  lens  he  was  able  to  see  minute  living  animal- 
cules in  saliva,  water,  and  other  fluids,  that  were 
smaller  than  any  seen  before.  The  descriptions  of  the 
animalcules  he  saw  were  very  accurate  and  correspond 
to  some  of  the  forms  we  recognize  today. 

The  discovery  of  these  minute  living  organisms  The  theory 


provoked    a    great    deal    of    discussion,    as    may    be 
imagined.      Perhaps  the  question   most   debated   was       tion 

CD 


2  BACTERIOLOGY. 

their  source  and  mode  of  origin.  Among  the  lowest 
forms  of  animal  life  known  at  that  time  were  the 
maggots  found  in  putrefying  meat.  It  was  supposed 
that  they  developed  from  the  meat  during  the  pro- 
cess of  putrefaction.  The  animalcules  of  von  Leeu- 
wenhoeck  too  were  believed  to  originate  spontane- 
ously. This  theory  of  spontaneous  generation  held 
sway  and,  although  there  were  many  opposed  to  this 
doctrine,  it  was  not  until  nearly  a  hundred  years  later 
that  Spallanzani  (1769),  an  Italian,  tried  by  experi- 
ment to  show  that  micro-organisms  could  not  develop 
in  this  way.  He  took  animal  matter  and  mixed  it  with 
Expert-  water  in  a  flask.  After  boiling  the  mixture  and  seal- 
proving  ing  the  neck  of  the  flask  he  found  that  it  could  be 

spontane- 

°eratkm  kept  for  a  long  time  without  putrefying  and  without 
incorrect  anv  micro-organisms  developing  in  it.  This  experi- 
ment was  subjected  to  much  criticism,  however,  be- 
cause the  air  so  essential  for  the  development  of  life 
was  excluded  by  sealing  the  flask.  This  objection 
was  met  by  modifying  the  experiment,  first  by  ad- 
mitting air  that  had  passed  through  strong  sulphuric 
acid,  and  later  by  filtering  the  air  through  cotton 
used  to  plug  the  mouth  of  the  flask.  It  remained  for 
Pasteur  (1860)  to  settle  the  question  beyond  dispute 
by  showing  that  the  entrance  of  dust  into  mixtures 
that  had  been  boiled  was  sufficient  to  set  up  putre- 
faction on  account  of  the  germs  carried  in  with  it. 
So  long  as  the  air  was  filtered  free  of  germs  by  cot- 
ton plugs,  just  so  long  the  mixtures  remained  free 
from  growth. 


HISTORY  OF  BACTERIOLOGY.  3 

These  experiments  had  a  far-reaching  influence 
upon  the  conception  of  bacteriology,  as  may  be  imag- 
ined, and  proved  beyond  question  that  germs  originate 
only  from  germs.  Upon  this  fact  rest  all  our  ideas 
of  preventing  the  spread  of  disease  and  the  aseptic 
precautions  used  in  surgery. 

The  association  of  micro-organisms  with  the  pro- 
duction  of  disease,  conceived  long  before  the  organ- 
isms  were  seen,  received  much  attention  after  the 
observations  of  von  Leeuwenhoeck.  During  the  next 
hundred  years  all  sorts  and  kinds  of  disease  were  one 
after  another  attributed  to  the  growth  of  germs  in 
the  body.  Von  Plenciz  (1762),  a  physician  of 
Vienna,  was  perhaps  the  foremost  advocate  of  these 
new  ideas  of  the  causation  of  disease.  He  believed 
not  only  that  germs  gave  rise  to  some  diseases,  but 
that  each  disease  had  its  own  particular  germ  which, 
after  entering  the  body,  developed  and  multiplied. 
These  theories  of  von  Plenciz  were  subjected  to 
much  ridicule,  to  be  sure;  but  they  continued  to  gain 
adherents  nevertheless,  and  have  proven,  as  we  know, 
to  be  correct.  Some  years  later  Henle  (1840)  col- 
lected and  published  all  the  work  that  had  been  done 
up  to  that  time,  and  pointed  out  that  the  causal 
relationship  of  germs  to  disease  could  not  be  proven 
simply  by  finding  germs  in  the  diseased  tissues  of 
the  body,  but  that  they  must  also  be  grown  and 
studied  outside  of  the  body.  Experiments  to  prove 
the  doctrines  of  Henle  were  lacking  chiefly  because 


4  BACTERIOLOGY. 

the  instruments  and  methods  for  studying  germs  at 
that  time  were  inadequate. 

In  the  next  thirty  to  forty  years  many  new 
methods  were  introduced  which  marked  a  rapid 
progress  in  the  study  of  germs;  for  example,  the 
use  of  aniline,  dyes  for  coloring  germs  so  that  they 
could  be  seen  better  under  the  microscope,  and  solid 
culture  media  on  which  germs  could  be  cultivated 
and  different  kinds  separated  and  studied.  The  de- 
velopment of  these  new  methods  was  due  chiefly  to 
the  genius  of  Koch,  who  also  laid  down  certain  laws 
or  conditions  which  had  to  be  fulfilled  before  any 
germ  could  be  said  to  be  the  cause  of  any  specific 
disease.  With  improved  methods  and  appliances  the 
relationship  of  germs  to  specific  diseases  could  be 
proven  experimentally,  and  the  discovery  of  the 
germs  o>f  many  diseases  followed  with  great  rapidity. 
Since  1879  the  germs  causing  the  following  diseases 
have  been  discovered :  Diphtheria,  Leprosy,  Typhoid 
Fever,  Tuberculosis,  Tetanus  (Lockjaw),  -  Influenza, 
Bubonic  Plague,  Cholera,  Meningitis,  Pneumonia, 
Syphilis,  Gonorrhea,  and  others. 

The  study  of  the  life  history  or  biology  of  these 
germs  has  led  to  our  present  knowledge  of  the 
cause,  the  course,  and  ways  of  preventing  most  of 
the  infectious  diseases,  and  has  put  into  the  hands 
of  physicians  the  means  whereby  the  character  of  an 
infectious  disease  may  be  detected. 

From  this  brief  sketch  it  is  easy  to  appreciate 
that  bacteriology  is,  comparatively  speaking,  a  new 


HISTORY  OF  BACTERIOLOGY.  5 

science,  and  that  its  greatest  progress  has  occurred 
in  our  time.  It  is  advancing  now  even  more  rapidly 
than  ever  before  along  lines  destined  to  be  of  the 
greatest  service  to  humanity.  Efforts  are  being  di- 
rected particularly  to  the  discovery  of  antitoxins  and 
serums  that  will  protect  against  the  infectious  dis- 
eases. 


CHAPTER  II. 


Classi- 
fication   of 
bacteria 


Definition 
of  bac- 
terium 


Structure 


THE  CLASSIFICATION,  MORPHOLOGY,  BIOLOGY,  AND 
DISTRIBUTION  OF  BACTERIA. 

WE  have  referred  to  microorganisms  as  germs, 
a  popular  term,  but  not  exact  enough  for  our  use. 
The  term  "germs"  may  be  taken  to  mean  any  micro- 
scopic organism,  animal  or  vegetable. 

In  the  animal  kingdom  the  lowest  forms  of  life 
are  called  Protozoa  (sing.  Protozoon),  of  which 
there  are  several  types:  Sarcodina,  Mastigophora, 
and  Sporozoa.  The  discussion  of  the  protozoa  will 
be  reserved  until  a  later  chapter. 

In  the  vegetable  kingdom  we  are  particularly 
interested  in  the  fungi,  which  are  subdivided  into 
Hyphomycetes  or  molds,  Blastomycetes  or  yeasts, 
and  Schizomycetes  or  bacteria.  The  bacteria  are  by 
far  the  most  important  of  the  three;  so  we  will  con- 
fine ourselves  solely  to  them  for  the  present,  and 
leave  the  yeasts  and  molds  for  a  subsequent  chapter. 

The  word  bacterium  is  derived  from  a  Greek 
word  meaning  a  rod;  the  plural  form  is  bacteria.  A 
bacterium  may  be  defined  as  a  minute  living  organ- 
ism composed  of  one  cell,  belonging  to  the  vegetable 
kingdom. 

The  structure  of  bacteria  is  very  simple  as  we 
know  it.  The  vital  part  of  the  cell  which  controls 
its  activities  is  called  the  nucleus,  and  is  usually  situ- 
ated at  or  near  the  center.  Surrounding  this  is  a 
(6) 


Fig.  1.— Different  forms  of  bacteria.    /4,  cocci ;  B,  bacilli ; 
C,  spirilla.     (Baumgarten.) 

(7) 


8  BACTERIOLOGY. 

transparent  and  homogeneous  substance  called  the 
protoplasm,  which  takes  up  the  nutriment  from  with- 
out. At  the  periphery  the  protoplasm  becomes  denser 
and  forms  what  is  known  as  the  capsule  of  the  cell. 
The  amount  of  protoplasm  is  very  small,  so  that 
under  the  microscope  there  appears  to  be  only  nucleus 
and  capsule. 

The  morphological  characters  of  bacteria; — that 
is,  their  size  and  shape — vary  greatly,  and  upon  this 
basis  it  is  convenient  to  subdivide  them,  into  three 
types:- 

Mor- 

A.  Coccus;  plural  form,  Cocci. 

B.  Bacillus;  plural  form,   Bacilli. 

C.  Spirillum;  plural  form,  Spirilla. 

The  cocci. are  shaped  like  berries,  that  is,  about 
spherical.  They  may  be  flattened  on  one  side  or 
concave,  or  split  like  a  coffee-bean.  They  may  be 
arranged  in  pairs  called  diplococci;  in  fours,  tetra- 
cocci ;  or  in  cubes,  sarcinse.  They  are  commonly  ar- 
ranged in  long  strings  or  chains  termed  streptococci, 
or  in  masses,  often  likened  to  bunches  of  grapes, 
staphylococci.  The  bacilli  are  rod-shaped,  sometimes 
slightly  curved,  and  vary  greatly  in  length,  from 
Viooo  to  1/25ooo  °f  an  mcn-  They  occasionally  form 
in  chains  or  rows.  The  spirilla  are  spiral  or  cork- 
screw-shaped, as  the  name  implies.  They  vary  both 
in  length  and  in  the  number  of  spirals.  Of  these 
three  types  the  bacilli  are  by  far  the  most  numerous 
and  the  spirilla  the  least  numerous.  The  types  are 


CLASSIFICATION  OF  BACTERIA.  9 

not  interchangeable;  so  it  is  not  possible  for  a  coccus 
to  become  a  bacillus  or  a  bacillus  a  spirillum. 

In  order  to  see  them  it  is  necessary  to  use  a 
microscope  of  high  magnifying  power;  indeed,  it  is 
highly  probable  that  some  forms  of  bacteria  are  so 
small  that  they  cannot  be  seen  with  any  of  the  micro- 
scopes that  we  have. 

Bacteria  reproduce  by  what  is  known  as  binary  |^ecpt™ 
fission;  that  means  a  pinching  off  or  splitting  in  the 
middle,  each  part  developing  into  another  organism. 
Reproduction  occurs  only  under  conditions  favorable 
for  bacterial  growth.  The  rate  of  division  or  multi- 
plication is  very  fast,  sometimes  every  fifteen  minutes. 
Starting  with  one  organism  one  can  imagine  what  an 
enormous  number  may  develop  in  twenty-four  hours 
at  this  rate. 

Under  conditions  unfavorable  to  the  life  and 
growth  some  kinds  of  bacteria  may  assume  another 
form  to  avoid  extermination.  This  is  called  spore 
formation.  These  spores  are  round  or  oval  bodies, 
much  smaller  than  the  organism  from  which  they 
originate,  and  differ  from  them  in  having  a  thick 
protective  capsule  that  enables  them  to  withstand 
heat,  sunlight  and,  in  fact,  any  harmful  influence. 
The  spores  may  be  formed  inside  the  body  of  the  fo{?£fa 
organism  and  extruded  from  it,  or  the  whole  organ- 
ism may  be  changed  into  a  spore.  As  a  rule,  one 
spore  forms  in  each  organism,  but  in  some  kinds  of 
bacteria  several  may  be  formed.  When  conditions 
again  become  favorable  for  growth  the  spore  may 


10  BACTERIOLOGY. 

elongate  and  gradually  assume  its  original  shape,  or 
the  bacillus  may  form  inside  the  body  of  the  spore  and 
burst  the  capsule.  (See  Fig.  9.) 

Motiiity  The  p0wer  of  .locomotion  is  observed   in   some 

bacteria.  When  watched  under  the  microscope  they 
may  be  seen  moving  across  the  field  of  vision.  The 
motility  depends  upon  small,  threadlike  processes  pro- 
jecting from  the  bodies  of  the  bacteria,  called  flagella 
(singular  form,  flagellum),  which  by  moving  to  and 
fro  with  a  whiplike  motion  propel  the  bodies  forward. 
The  flagella  may  be  single  or  multiple,  and  may  be 
placed  at  one  or  both  ends  or  all  around  the  bac- 
terium. The  motility  of  spirilla  is  somewhat  differ- 
ent. The  amount  of  protoplasm  about  the  nucleus  is 
much  more  abundant  than  in  the  bacilli,  and  this  by 
an  undulating,  wavelike  motion  drives  the  organism 
forward.  The  phenomenon  of  locomotion  is  limited  to 
bacilli  and  spirilla;  the  cocci  do  not  move.  (See 
Fig.  6,  page  57.) 

The  property  of  producing  pigment  or  coloring 
matter  is  peculiar  to  some  kinds  of  bacteria.  The 
pigment  may  be  entirely  within  the  body  of  the 
organism  or  it  may  be  set  free  from  it  and  color  the 
^e°speof  material  upon  which  the  bacteria  are  growing.  Other 
bacteria  properties  of  bacteria  that  may  be  mentioned  are  the 
fermentation  of  sugars  into  alcohol,  the  production 
of  characteristic  odors,  the  formation  of  acids  and 
alkalies,  and  the  production  of  light.  The  property 
of  producing  poisons  is  perhaps  the  most  important 
of  all,  and  will  be;  spoken  of  in  detail  in  the  chapter  on 
immunity. 


BIOLOGY  OF  BACTERIA.  H 

From  what  has  been  said  of  the  properties  of 
bacteria  it  is  possible  to  make  a  number  of  classifica- 
tions; for  example,  there  are  the  spore-forming  and 
non-spore-forming  bacteria,  the  motile  and  non-motile, 
fermenting  and  non-fermenting,  acid  forming  and 
alkali  forming,  etc.  By  observing  these  properties  of 
bacteria  it  is  possible  to  identify  them. 

Like  all  plants  bacteria  require  food,  which  must  Nutriment 
be  in  very  simple  form  to  enable  them  to  assimilate  it. 
Oxygen,  carbon,  nitrogen,  hydrogen,  and  chemical 
salts  form  their  chief  food.  They  derive  the  oxygen 
from  the  air,  although  some  varieties  of  bacteria  take 
it  from  substances  in  which  the  oxygen  is  combined 
with  other  chemical  elements.  The  bacteria  that  take 
their  oxygen  from  the  air  are  called  aerobic  bacteria, 
while  those  taking  it  from  substances  containing  it  in 
combined  form  are  called  anaerobic  bacteria.  The  line 
o<f  demarcation  between  the  aerobic  and  the  anaerobic 
bacteria  is  not  fixed,  as  sometimes  bacteria  thriving 
best  under  aerobic  conditions  will,  nevertheless,  grow 
in  the  absence  of  free  oxygen  and  vice  versa.  These 
are  spoken  of  as  facultative  anaerobes  or  aerobes,  as 
the  case  may  be.  The  carbon  is  obtained  from  pro- 
teids,  carbohydrates  (starchy  substances),  or  fats. 
The  hydrogen  is  derived  for  the  most  part  from,  water. 
The  nitrogen  is  obtained  from  proteids  such  as  albumin. 
The  salts  required  for  nutrition  are  sodium,  potas- 
sium, and  magnesium. 

Certain  conditions  of  environment  exert  a  great 
deal  of  influence  upon  the  life  and  growth  of  bacteria. 


12  BACTERIOLOGY. 

influence    The    influence    of    temperature    is    most    important. 

ronment  Bacteria  thrive  best  at  37.5°  C,  and  as  the  temperature 
varies  above  or  below  this  point  growth  is  retarded. 
A  temperature  of  62°  C.  will  kill  most  bacteria.  Low 
temperatures  are  not  so  destructive,  for  by  experiments 
it  has  been  proven  that  a  temperature  of  200  degrees 
below  zero  (centigrade)  will  not  kill  all  bacteria. 

Moisture  is  essential  for  the  growth  of  bacteria, 
as  the  food  material  upon  which  bacteria  thrive  must 
be  in  solution.  The  reaction  of  the  food  material  is 
of  considerable  moment,  for  bacteria  will  not  grow  if 
too  much  acid  or  alkali  is  present.  A  neutral  or 
slightly  acid  reaction  gives  the  best  growth. 

cuitiva-  ln  order  to  cultivate  bacteria,  substances  must  be 

tion 

used  from  which  they  can  obtain  the  proper  nutriment. 
Such  substances  when  made  artificially  are  called  cul- 
ture media,  and  they  may  be  solid  or  fluid.  The  solid 
media  are  employed  when  a,  surface  growth  is  desired, 
the  bacteria  being  rubbed  on  the  surface.  The  com- 
mon kinds  of  solid  media  are  agar-agar,  gelatin,  and 
coagulated  blood-serum.  Fluid  media  are  used  for 
the  determination  of  acid  formation,  fermentation, 
coagulation,  and  motility;  those  most  often  used  are 
milk  and  bouillon.  The  media  are  prepared  in  the 
laboratory.  After  the  ingredients  have  been  dissolved 
by  boiling,  the  whole  is  filtered,  run  into  test-tubes, 
plugged  with  cotton,  and  finally  sterilized  by  steam 
under  pressure  in  order  that  no  bacteria  may  develop 
in  it  except  those  introduced  for  the  purpose  of  study. 
The  distribution  of  bacteria  in  nature  is  prac- 


DISTRIBUTION  OF  BACTERIA.  13 

tically  universal.     They  are  found  in  the  soil,  in  the      Distn- 

<f  bution 

air,  in  the  food  we  eat,  and  in  the  water  we  drink.  In 
fact,  wherever  plants  and  animals  live,  bacteria  are 
found.  Their  distribution,  however,  is  not  equal,  being 
more  numerous  in  some'  places  than  others.  The  soil 
is  the  chief  home  of  bacteria  on  account  of  the  large 
amount  of  animal  matter  in  it.  They  are  present  in 
greatest  number  at  the  surface  and  diminish  in  the 
deeper  layers.  The  reason  for  this  is  that  the  closely 
packed  particles  of  the  soil  will  not  permit  the  bacteria 
to  penetrate  beyond  the  superficial  layers.  Surface 
water  which  contains  bacteria  in  great  number  is 
rendered  practically  free  from  them  by  this  filtering 
action  of  the  soil. 

In  the  air  the  number  of  bacteria  is  directly  pro-  AIr 
portional  to  the  amount  of  dust.  When  the  wind 
blows  the  dust  into  the  air,  large  numbers  of  bacteria 
are  carried  with  it ;  but  wheni  the  air  is  quiet,  the  bac- 
teria by  force  of  gravity  settle  to  the  ground.  It  is  a 
well-known  fact  that  bacteria  will  not  leave  a  moist 
surface;  so  in  wet  weather  the  number  of  bacteria  in 
the  air  is  considerably  less  than  at  other  times.  At 
high  altitudes  and  far  out  at  sea  there  are  practically 
no  bacteria  in  the  air,  as  there  is  no>  dust.  The  bacteria 
in  the  soil  and:  air  do  not  exist  as  a  rule  in  their  tru 
form,  but  as  spores  which  develop  into  bacteria  when 
the  conditions  for  growth  become  favorable. 

Water  as  it  leaves  the  clouds  in  the  form  of  rain      water 
is  free  from  bacteria,  but  as  the  rain-drops  approach 
the  earth  particles  of  dust  adhere  to  them!.     After  the 


14  BACTERIOLOGY. 

rain  becomes  mixed  with  the  soil,  the  number  of  bac- 
teria present  is  very  large. 

Foods  become  contaminated  with  bacteria  in  a 
variety  of  ways.  Vegetables  always  have  the  soil 
bacteria  on  their  surface.  Meats  if  exposed  to  the 
air  take  up  bacteria  from  the  dust.  The  surfaces  of 
fruits  become  contaminated  with  bacteria  in  the  same 
way.  In  order  to  diminish  the  contamination  of  foods 
as  much  as  possible,  ordinances  are  in  force  in  .many 
cities  that  require  meats,  fruits,  candies,  etc.,  to  be 
covered  with  glass  when  displayed  for  sale. 
tkXinCo~f  With  bacteria  so  widely  distributed  on  the  earth, 

erlf  the  question  arises  as  to  their  use  or  function  in  the 
world.  We  are  accustomed  to  think  of  bacteria  solely 
as  the  cause  of  disease,  and  offhand  we  would  say  that 
this  was  their  chief  function.  This  is  not  true  by  any 
means,  for  instead  of  being  harmful  to  life  they  are 
very  beneficial;  in  fact,  life  could  not  be  maintained 
without  them.  The  causation  of  disease  is  a  function 
limited  to  a  small  group  of  micro-organisms,  and  is 
of  lesser  importance.  The  much  more  important  use 
of  bacteria  relates  to  their  ability  to  produce  sub- 
stances called  ferments  or  enzymes,  which  have  the 
property  of  reducing  complex  organic  compounds  into 
simpler  compounds  and  chemical  elements. 

The  plants  which  form  the  food  of  animals  would 
soon  be  exhausted  unless  they  could  obtain  proper 
nutriment  to  sustain  life  and  reproduce  their  kind. 
They  live  mainly  upon  carbon  and  nitrogen  in  the  form 
of  nitrates,  which  would  soon  be  consumed  from  the 


BACTERIA.  15 

soil  unless  the  supply  was  continually  replenished. 
Now,  the  source  of  carbon  and  nitrogen  is  the  excre- 
tions and  secretions  of  animals,  which  contain  these 
elements  in  combination  with  other  elements.  By  the 
action  of  bacteria  the  complex  animal  matter  is  de- 
composed into  the  chemical  elements  that  compose  it. 
In  this  way  the  plants  derive  their. carbon  and  nitro- 
gen from  the  soil.  Within  the  body  the  bacteria  carry 
on  much  the  same  activities.  The  digestion  and  ab- 
sorption in]  the  intestine  is  dependent  to  a  large  extent 
on  the  breaking-down  action  of  bacteria.  We  cannot 
absorb  meat  and  vegetable  as  such,  and  it  is  only  after 
our  food  has  been  separated  into  simple  compounds 
and  elements  that  it  is  absorbed  to  nourish  the  body. 
In  this  process  the  bacteria  play  no>  small  part.  But 
bacteria  are  not  only  agents  capable  of  breaking  down 
complex  substances;  they  also  build  up  substances 
from  chemical  elements.  Some  plants  take  their  nitro- 
gen from  the  air,  but  they  would  not  be  able  toi  do  so 
were  it  not  for  the  presence  of  certain  bacteria  grow- 
ing* in  the  roots. 

The  maintenance  of  life  in  the  world  is  often 
described  as  a  cycle;  first,  the  chemical  elements  are 
built  up  into  plants,  the  plants  nourish  the  animals, 
then  the  animal  tissue  is  consumed  and  excreted  to  be 
broken  down  into  elements.  In  each  step  the  bacteria 
play  a  most  important  part. 

These  activities  of  bacteria  and  their  enzymes  are    commer- 

t  /.  .    ...  .  cial    use 

made  use  of  commercially;  the  fermenting  action  on     of  bac- 
sugars  converting  them  into  alcohol  is  used  in  making 


16  BACTERIOLOGY. 

beer  and  wine,   the  clotting  of  milk  by  bacteria   in 
making  cheese,  the  fermenting  of  cabbage  in  making 
sauerkraut. 
Pto-  It  may  be  well  to  mention  here  certain  substances 

mames 

that  are  formed  principally  in  the  decomposition  of 
meat  and  fish  by  bacteria.  They  are  called  ptomaines, 
and  are  present  in  partially  decomposed  animal  and 
vegetable  matter.  Some  of  them  are  highly  poisonous. 
The  most  common  poisonous  ptomaines  are  those 
found  in  partially  decomposed  meat,  fish,  and  ice-cream. 


CHAPTER  III. 

THE   DESTRUCTION    OF   BACTERIA,    STERILIZATION 
AND  DISINFECTION. 

THE  knowledge  of  the  means  by  which  bacteria 
are  destroyed  underlies  the  methods  employed  in  dis-    dlstk>fnec~ 
infection,  sterilization,  and  antisepsis  as  they  are  used 
in  preventing  the  spread  of  infection.     The  term  dis- 
infection means  the  total  destruction  of  bacteria  by 
any  agent,  while  sterilization  is  limited  to  the  destruc-     sterili. 
tion  of-  bacteria  by  heat.     An  antiseptic  is  a  chemical    and^nti- 
agent  that  prevents  the  growth  and  multiplication  of 
bacteria,  but  does  not  necessarily  destroy  them.     A 
deodorant  is  a  substance  that  masks  offensive  odors 
or  substitutes  an  agreeable  odor  for  a  disagreeable 
one.    Some  of  the  disinfectants  and  antiseptics  are  also 
deodorants,   but   few   of   the   deodorants   have   disin- 
fectant properties. 

The  agents  that  affect  bacteria  injuriously  may    Physical 
be  physical  or  chemical.     Among  the  physical  agents 
may  be  mentioned  drying,  light,  and  heat. 

Drying  prevents  the  growth  of  bacteria  and  will 
eventually  destroy  them.  The  spores  of  bacteria,  how- 
ever, will  resist  drying  for  a  much  longer  time.  It  is 
for  this  reason  that  the  bacterial  content  of  dust  is 
chiefly  in  the  form  of  spores.  The  effect  of  drying  is 
influenced  by  the  temperature  at  which  the  drying 

2  (17) 


18  BACTERIOLOGY. 

takes  place,  being  much  more  injurious  at  high  than  at 
low  temperature. 

sunlight  Sunlight  is  a  very  powerful  and  effective  agent 

for  destroying  bacteria.  By  experiment  it  has  been 
proven  that  the  tubercle  bacillus,  the  cause  of  con- 
sumption, is  killed  by  sunlight  in  two  hours  or  less, 
depending  upon  the  thickness  of  the  material  surround- 
ing it.  The  effect  of  electric  light  and  the  X-ray 
is  very  much  less  powerful  than  sunlight,  and  to  be 
effective  must  be  concentrated  and  allowed  to  act  for  a 
greater  length,  of  time. 

Heat  Heat  is  the  most  powerful  of   all  the  physical 

agents.  Its  destructive  action  is  dependent  upon  the 
degree  of  temperature  and  the  length  of  time  it  is 
applied;  the  higher  the  temperature,  the  less  the  time 
required.  It  may  be  employed  either  as  dry  or  moist 
heat.  Dry  heat  is  used  in  the  sterilization  of  glassware, 
such  as  flasks,  test-tubes,  swabs,  and  pipettes.  The 
temperature  should  reach  140°  to  150°  C,  and  must 
be  allowed  to  act  for  one  hour  in  order  to  effect  sterili- 
zation. The  instrument  used  for  this  purpose  is  called 
a  dry-heat  sterilizer,  and  consists  of  a  double-walled 
box,  made  of  sheet  iron  and  asbestos.  An  opening  in 
the  top  admits  a  thermometer  by  which  the  temperature 
of  the  inner  chamber  may  be  measured.  The  flame, 
usually  a  triple  Bunsen  burner,  generates  the  heat 
underneath,  which  circulates  between  the  walls  of  the 
box,  keeping  the  temperature  even  on  all  sides. 

For  sterilizing  all  sorts  of  surgical  instruments, 
except  those  with  cutting  edge,  moist  heat  is  used.     It 


DESTRUCTION  OF  BACTERIA. 


19 


is  more  effective  than  dry  heat,  because  it  has  greater 
penetration.  Boiling  for  five  minutes  will  destroy  all 
forms  of  bacteria  except  spores,  which  require  boiling 
for  two  hours.  The  destructive  action  is  intensified 
and  the  danger  of  rusting  avoided  if  sodium  carbonate 


Fig.  2. — Arnold's  steam  sterilizer. 

is  added  to  the  water  in  amount  sufficient  to  make  a 
i  per  cent,  solution.  Live  steam  is  employed  for  steril- 
izing dressings.  The  instrument  most  often  used  is 
the  Arnold  sterilizer,  which  consists  of  two*  metal 
chambers,  one  within  the  other,  beneath  which  is  a  pan 
containing  the  water  to  be  heated.  A  flame  under- 
neath boils  the  water  and  generates  the  steam,  which 
rises  to  the  upper  chamber  and  penetrates  the  contents. 
The  exposure  of  dressings  in  this  way  to  live  steam 


Boiling 


Steam 


20  BACTERIOLOGY. 

Frac-      will  kill  bacteria  in  thirty  minutes,  but  not  their  spores. 

steriii-  In  order  to  destroy  the  spores  fractional  sterilization  is 
employed.  This  is  done  by  sterilizing  for  thirty 
minutes  on  three  successive  days.  By  the  first  exposure 
the  bacteria  are  killed,  but  the  spores  that  may  be 
present  are  not.  The  dressings  are  now  allowed  to 
stand  for  twenty-four  hours  at  roomi  temperature  in 
order  to  allow  the  spores  to  develop  into  bacteria, 
when  another  exposure  of  thirty  minutes  is  made. 
This  is  repeated  at  the  end  of  another  twenty-four 
hours.  At  the  end  of  the  third  exposure  it  is  presumed 
that  all  spores  have  developed  into  bacteria,  and  that 
all  bacteria  have  been  destroyed  by  steam.  Live  steam 
is  also  used  for  killing  bacteria  in  milk,  and  will  be 
considered  later, 
zafion^by  -^7  ^ar  tne  miOSt  effective  method  of  sterilizing  by 

unde?  heat  is  the  use  of  steam  under  pressure.  The  action  of 
the  steam  is  intensified  and  its  penetrating  power  in- 
creased by  the  pressure.  The  instrument  used  is  called 
an  autoclave.  It  consists  of  a  double-walled  cylinder 
or  globe  made  of  metal,  with  a  steam  gauge  and  vent 
at  the  top.  The  materials  to  be  sterilized  are  placed 
in  the  inner  chamber,  the  door  closed,  and  the  steam 
allowed  to  enter  the  outer  jacket.  The  vent  at  the  top 
is  left  open  until  the  steam  has  forced  out  all  the  air, 
as  air  interferes  with  the  action  of  the  steam.  After 
closing  the  vent  the  steam  is  forced  into  the  inner 
jacket  until  the  gauge  shows  a  pressure  of  15  pounds, 
or  one  atmosphere,  and  allowed  to<  remain  so  for 
fifteen  to  twenty  minutes.  This  exposure  will  kill  all 


DESTRUCTION  OF  BACTERIA.  21 

bacteria  and  spores.  If  any  fluid  contained  in  flasks 
or  test-tubes  is  being  sterilized,  care  must  be  taken  that 
the  steam  be  allowed  to  escape  gradually  at  the  end  of 
the  exposure,  otherwise  the  suction  will  draw  the  plugs 


Fig.  3.— Autoclave.     (A.  H.  T.  Co.) 

from  them.  Much  larger  sterilizers  which  embody  the 
same  principles  as  the  one  just  described  are  used  by 
hospitals,  quarantine  stations,  and  departments  of 
health  in  cities  for  disinfecting  wearing  apparel,  bed- 
clothing,  and  bedding. 


22  BACTERIOLOGY. 

chemical  The  number  of  chemical  agents  having  destruct- 

agents         .  .  , 

ive  action  on  bacteria  is  very  large,  and  no  attempt 
will  be  made  to  speak  of  them  all.  It  will  suffice  to 
mention  a  few  of  the  most  common  ones,  and  describe 
the  way  they  may  be  applied  best.  Chemical  disin- 
fectants may  be  used  dry,  in1  solution,  or  in  the  form 
pry  dis-  of  gas.  As  examples  of  dry  disinfectants,  boric  acid, 

infection         .  . 

bismuth,  and  lodoform  may  be  mentioned.  All  are 
used  in  concentrated  form  as  they  are  obtained  com- 
mercially. Boric  acid  and  bismuth  are  weakly  bac- 
tericidal, and  have  an  antiseptic  rather  than  a  disin- 
fectant action.  lodoform  when  iodine  is  set  free  is 
disinfectant.  Their  chief  use  is  on  infected  wounds. 

Some  of  the  most  used  disinfectant  solutions  are 
as  follows: — 

Disin-          Formalin   (a  40%   solution  of 

fectant 

solutions  formaldehyde  gas  in  water)  .  10  to  20  %. 

Bichloride  of  mercury i :  500  to  i :  1000. 

Carbolic  acid    5%. 

Chlorinated   lime    (chloride  of 

lime)    5%  (6  oz.  to  gal.). 

Hydrogen  peroxide 20%. 

Alcohol   70%. 

Not  all  of  these  solutions  are  equally  efficacious 
for  disinfecting,  and  each  one  has  its  advantages  and 
disadvantages. 

Formalin  is  an  excellent  disinfectant,  and,  in 
addition,  is  also  a  good  deodorant.  It  does  not  injure 
fabrics,  is  not  poisonous,  and  does  not  coagulate  albu- 


DESTRUCTION  OF. BACTERIA.  23 

min.  It  is  liable  to  rust  iron  and  steel.  It  is  suitable 
for  the  disinfection  of  urine,  sputum,  feces,  and  albu- 
minous discharges.  It  is  not  a  good  skin  disin- 
fectant because  it  hardens  the  skin  and  in  some  cases 
will  cause  a  dermatitis. 

Bichloride  of  mercury  is  of  limited  usefulness 
because  it  is  a  corrosive  poison,  corrodes  all  metals, 
and  coagulates  albumin.  This  last  action  renders  it  of 
little  use  for  the  disinfection  of  sputum,  feces,  or  pus. 
On  the  other  hand,  it  is  excellent  for  disinfecting 
floors,  walls,  and  furniture;  that  is,  surface  disinfec- 
tion. In  the  strength  of  i :  1000  it  kills  bacteria  in  a 
half  an  hour,  but  for  spores  a  i :  500  solution  must  be 
used.  It  is  widely  used  for  skin  disinfection;  for  this 
purpose  a  1 :  1000  solution  is  sufficiently  strong.  On 
account  of  the  poisonous  property  of  bichloride  solu- 
tions it  is  safer  to  add  coloring  material  to  prevent  any 
possibility  of  their  being  drunk  by  mistake. 

Carbolic  acid  is  suitable  for  the  disinfection  of 
intestinal  discharges,  sputum,  urine,  floors,  furniture, 
soiled  linen,  and  clothing.  It  will  coagulate  albumin, 
but  its  action  is  not  interfered  with  to)  so>  great  an 
extent  as  is  the  case  with  bichloride,  of  mercury. 
Cresols,  chemical  substances  closely  related  to  carbolic 
acid,  are  more  powerful  and  not  so  poisonous.  They 
may  be  used  in  5  per  cent,  solution. 

Chlorinated  lime  is  a  deodorant  as  well  as  a  dis- 
infectant, both  properties  being  dependent  upon  the 
liberation  of  chlorine  gas  in  the  presence  of  moisture. 
It  is  most  widely  known  a.nd  used  for  the  disinfec- 


24  BACTERIOLOGY. 

tion  of  intestinal  discharges  of  typhoid-fever  patients. 
It  undergoes  decomposition  readily;  so  care  must  be 
taken  that  it  be  fresh  if  good  results  are  expected.  For 
disinfecting  stools  the  amount  of  lime  solution  should 
be  much  in  excess  of  the  volume  of  the  stool,  and  it 
should  be  allowed  to  act  for  several  hours.  It  can  be 
used  also  for  disinfecting  floors  and  woodwork,  but 
should  not  be  used  on  colored  fabrics,  as  it  is  a  power- 
ful bleacher. 

Hydrogen  peroxide  decomposes  readily,  giving 
off  free  oxygen,  upon  which  its  disinfecting  action 
depends.  It  is  used  to  a  large  extent  for  destroying 
the  pus  bacteria  of  superficial  wounds,  and  is  an  ex- 
cellent mouth  disinfectant. 

Alcohol,  either  absolute  or  in  95  per  cent, 
strength,  is  weakly  disinfectant.  The  addition  of 
water  seems  to  add  to  its  disinfecting  action.  Solu- 
tions of  50  to  70  per  cent,  are  best.  The  use  of  alcohol 
is  limited.  Perhaps  its  greatest  usefulness  is  in 
destroying  bacteria  in,  the  skin,  although  even  for  this 
it  is  rarely  depended  upon  alone. 

octant  Of  *ne  disinfectant  gases  only  the  two  most  often 

gases  use(j  neecj  j^  mentio,ned :  Sulphur-dioxide  gas  is  made 
by  burning  roll  sulphur  in  the  presence  of  water  vapor. 
The  vapor  is  essential  because  the  disinfectant  action 
depends  upon  the  formation  of  sulphurous  acid,  which 
is  made  by  the  combination  of  the  water  vapor  with 
the  fumes  of  sulphur.  It  requires  about  8  pounds  of 
sulphur  for  every  3000  cubic  feet  of  air  space,  and  it 
should  be  allowed  to  act  for  at  least  twenty-four  hours. 


DESTRUCTION  OF  BACTERIA.  25 

It  is  a  surface  disinfectant  having  very  little  pene- 
trating power,  and  is  not  as  reliable  as  it  was  once 
thought  to  be.  It  is  liable  to  corrode  fabrics  and 
destroy  colors.  It  tarnishes  metals  and  leaves  a  dis- 
agreeable odor  for  some  time  after  it  is  used. 

Formaldehyde  gas  is  made  in  a  variety  of  ways. 
For  use  in  hospitals  and  by  boards  of  health  an  auto- 
clave is  used,  which  generates  the  gas  under  pressure. 
After  the  room  has  been  sealed  to  prevent  the  gas 
from  escaping,  the  gas  from  the  autoclave  is  forced 
into  the  room  through  the  keyhole  of  the  door.  A 
much  simpler  way  that  is  practical  for  home  disin- 
fection is  the  burning  of  paraform  candles  in  the  pres- 
ence of  moisture.  The  disinfectant  action  is  strongest 
when  the  temperature  of  the  room,  is  between  90°  and 
100°  F.  The  gas  is  a  surface  disinfectant;  conse- 
quently, articles  to  be  disinfected  should  be  hung  up 
or  so  arranged  as  to  allow  the  free  circulation  of  the 
gas  about  them.  It  is  the  most  efficient  disinfectant 
known  when  properly  used,  and  is  also  a  deodorant. 
It  has  no  harmful  action  on  clothing  or  other  house- 
hold goods.  The  vapor  is  very  irritating  to  the  eyes 
and  upper  air-passages.  Although  the  gas  is  very 
destructive  to  bacteria  and  their  spores,  it  will  not 
kill  vermin. 

In  disinfecting  during  or  after  illness  of  con- 
tagious  or  infectious  nature,  it  is  necessary  to  render 
all  discharges,  excreta,  and  so  on,  non-infectious  and, 
at  the  conclusion  of  the  illness,  to  render  the  apart- 
ment in  which  the  patient  has  been  sick  safe  for  others 


26  BACTERIOLOGY. 

to  occupy.  In  practical  disinfection  the  choice  of  the 
disinfectant  should  be  governed  by  the  source  and 
character  of  the  material  to  be  disinfected,  and  by  the 
expense,  the  ease,  and  the  thoroughness  with  which 
the  disinfectant  may  be  applied. 

sputum  Sputum  always  contains  a  large  proportion  of 

mucus,  in  which  the  bacteria  are  imbedded.  In  order 
to  destroy  these  bacteria,  chemical  agents  of  con- 
siderable penetrating  power  are  required,  and  should 
be  allowed  to  act  for  considerable  periods  of  time. 
The  two  that  best  meet  these  requirements  are  for- 
malin, 10  per  cent,  solution,  and  carbolic  acid  in  5 
per  cent,  strength.  A  much  safer  way  is  to  collect  all 
sputum  in  paper  sputum-cups  or  paper  napkins  and 
then  burn  them.  This  way  has  been  in  use  a  long 
time  for  the  disposal  of  tuberculous  sputum,  but  it  is 
equally  as  practical  for  the  mouth  and  nasal  discharges 
of  diphtheria,  tonsillitis,  pneumonia,  and  cerebrospinal 
meningitis. 

Feces  Feces  can  be  quickly  and  thoroughly  destroyed  by 

burning  them  or  mixing  them  with  boiling  water.  If 
chemical  disinfectants  are  employed,  formalin  (10  per 
cent.)  or  carbolic  acid  (5  per  cent.)  may  be  used. 
The  amount  of  either  of  these  solutions  should  be 
twice  that  of  the  stool.  Chlorinated  lime,  so  long  used 
for  stool  disinfection,  has  no  advantages  over  formalin 
or  carbolic  acid,  and  is  not  so  easy  to  use.  The  urine 
may  be  disinfected  in  the  same  manner  as  the  stools. 
Clothing,  towels,  napkins,  and  bedding  should  be 
soaked  for  one-half  hour  in  a  5  per  cent,  solution  of 


DESTRUCTION  OF  BACTERIA.  27 

carbolic  acid  before  leaving1  the  sickroom  to  be  clothing 
laundered.  Dishes,  knives,  forks,  etc.,  should  be 
immersed  in  5  per  cent,  carbolic  solution  and  then 
boiled.  It  seems  hardly  necessary  to  say  that  one  set 
of  dishes  should  be  kept  in  the  sickroom  for  the  ex- 
clusive use  of  the  patient,  and  cleaned  there. 

Apartments  occupied  by  persons  sick  with  con- 
tagious  or  infectious  disease  should  not  be  occupied 
again  until  the  room  and  its  contents  have  been 
thoroughly  disinfected.  In  order  to  simplify  this 
procedure  a  little  forethought  on  the  part  of  the  nurse, 
in  removing  from  the  sickroom  all  articles  not  to  be 
used,  will  assist  a  great  deal.  Carpets,  upholstered 
furniture,  hangings,  pictures,  and  bric-a-brac  can 
easily  be  spared  from  the  room.  At  the  conclusion 
of  the  illness  by  far  the  most  effective  means  of  ren- 
dering the  room  free  from  infection  is  a  thorough 
scrubbing  of  everything  washable  with  soap  and  hot 
water,  a  continued  exposure  of  the  room)  to  fresh  air 
and  sunlight,  and  the  burning  of  everything  that  can- 
not be  washed  or  is  of  small  value.  The  effect  of  the 
scrubbing  is  increased  if  followed  by  a  solution  of  car- 
bolic acid  or  bichloride  solution.  If  arrangements 
cannot  be  made  to  have  the  mattress  sterilized  by 
steam  under  pressure  it  is  safer  to  burn  it. 

If  the  disinfection  of  the  apartments  by  gas, 
either  formaldehyde  or  sulphur,  is  to  be  employed,  it 
should  follow  the  cleansing  of  the  room  after  the 
manner  described  above.  The  room  must  first  of  all 
be  sealed  to  prevent  the  gas  from  escaping.  This  can 


28  BACTERIOLOGY. 

be  done  by  plugging  with  cotton  all  crevices  about  the 
windows  and  doors,  and  pasting  paper  over  radiators 
and  ventilators. 

Not  much  dependence  should  be  placed  on  gas 
disinfection  alone.  It  should  be  clearly  understood 
that  a  thorough  application  of  soap  and  water  and  free 
exposure  to  fresh  air  and  sunlight  are  much  to  be 
preferred  to  the  simple  introduction  of  formalin  gas 
or  any  other  disinfectant  without  due  regard  to  the 
proper  disposition  of  the  room  contents,  temperature, 
time  of  exposure,  and  the  quantity  of  the  disinfectant 
used.  The  careless  use  of  gas  disinfection  and  the 
popular  belief  that  filling  a  room  with  gas  kills  all  con- 
tagion have  led  to  disastrous  consequences,  and  are 
responsible  for  the  disrepute  into  which  disinfection 
has  fallen  in  some  quarters. 


CHAPTER  IV. 
INFECTION  AND  IMMUNITY. 
IN  the  preceding  chapters  we  have  been  dealing     Patho- 

...  genie  and 

with  the  subject  of  bacteriology  in  the  broadest  sense,  non-patno- 

J  **J  .       genie  bac- 

Attention  has  been  directed  to  the  function  of  bacteria  teria 
in  the  life  of  the  world,  to  their  appearance,  their 
manner  of  growth,  and  the  means  employed  for  their 
destruction.  As  physicians  and  nurses  our  interest 
centers  about  a  very  small  part  of  the  bacterial  king- 
dom, the  one  having  to  do  with  the  production  of 
disease.  Bacteria  that  produce  disease  are  termed 
pathogenic,  while  those  varieties  that  do  not  are 
called  non-pathogenic.  By  far  the  larger  number  of 
pathogenic  bacteria  thrive  only  in  the  living  tissues 
of  animals.  These  are  called  parasites.  Some  kinds 
of  bacteria  thrive  only  on  dead  tissues  or  wounded 
surfaces  and,  by  decomposing  them,  form  poisons 
(ptomaines)  which  may  be  absorbed  and  give  rise  to 
symptoms  such  as  fever,  chills,  and  headache.  These  infection 
are  termed  saprophytes.  When  pathogenic  bacteria 
gain  access  to  the  tissues  and  produce  injury  and 
symptoms,  we  say  that  infection  has  taken  place. 

Here  it  may  be  well  to  say  a  word  as  to  the  mean-     infec- 
ing  of  the  terms  "infectious"  and  "contagious."    They   ti0coSn-nd 
have  been  used  somewhat  loosely  and  have  led  to  a 
great  deal  of  confusion.     Any  disease  that  is  caused 
by   the   entrance    into  the   body   of   a   living   micro- 

(29) 


30  BACTERIOLOGY. 

organism  is  called  infectious.  As  examples  of  infec- 
tious disease,  diphtheria,  pneumonia,  influenza,  tuber- 
culosis, and  syphilis  may  be  mentioned ;  although  there 
are  many  others.  A  contagious  disease  is  one  that  is 
transmitted  from  one  person  to  another  through  the 
air  or  by  simply  coming  into1  the  presence  of  or  touch- 
ing the  sick.  Smallpox,  scarlet  fever,  measles,  chicken- 
pox,  and  German  measles  are  contagious.  All  con- 
tagious diseases  are  infectious,  but  not  all  infectious 
diseases  are  contagious.  Diseases  like  cholera,  gland- 
ers, pneumonia,  plague,  tuberculosis,  and  syphilis 
cannot  be  transmitted  through  the  air  or  by  coming 
into  the  presence  of  the  sick.  Typhoid  fever  may  be 
considered  infectious  through  water  and  other  infected 
foods,  and  contagious  by  contact  with  the  so-called 
typhoid  carriers. 

The  terms  "infestation"  or  "infestion"   are  ap- 
plied to  diseases  caused  by  the  entrance  into  the  body 
of  large  parasites  such  as  amebae,  worms,  and  so  on. 
Factors  While    the    presence    of   pathogenic    bacteria    is 

Ti?gein°~  necessary  to  cause  infection,  other  factors  of  much 
importance  must  be  taken  into  consideration.  This 
must  be  so,  as  every-day  experience  shows.  In  any 
epidemic  of  infectious  disease  only  a  portion  of  those 
exposed  become  infected.  Even  among  those  infected 
the  disease  presents  all  variations  from  the  very  mild 
to  the  most  severe.  The  factors  that  influence  the 
onset  and  course  of  infections  relate  both  to  the  bac- 
teria and  the  individuals  exposed  to  them. 

So  far  as  the  bacteria  themselves  are  concerned, 


INFECTION  AND  IMMUNITY.  31 

infection  depends  in  part  on  their  power  of  producing     on  the 

.  part  of 

disease,  that  is,  their  virulence.  Conditions  that  are  bacteria 
not  suited  to  the  growth  of  bacteria  will  diminish  or 
destroy  the  virulence ;  the  continued  cultivation  of  bac-  Viru_ 
teria  outside  the  body  on  artificial  culture  media  will 
do  this.  Bacteria  that  have  lost  the  power  of  pn>- 
ducing  disease  are  spoken  of  as  being  attenuated. 
Another  factor  that  modifies  infection  is  the  number  At^™a- 
of  bacteria  that  invade  the  tissues.  While  the  exact 
number  of  bacteria  necessary  to  cause  infection  is  not 
known,  it  may  be  said  that  the  greater  the  virulence 
the  fewer  the  bacteria  required.  The  path  by  which 
bacteria  enter  the  tissues  frequently  determines 
whether  infection  is  caused  or  not.  The  bacilli  of 
typhoid  fever  to  cause  infection  must  be  swallowed, 
but  if  they  are  rubbed  into  the  skin  no  infection  results. 
On  the  other  hand,  the  pus-forming  bacteria  like  the  0AVinfe?- 
staphylococci  and  streptococci  may  be  swallowed  with- 
out causing  infection,  but  if  they  are  rubbed  into  the 
skin  a  boil  or  an  abscess  is  almost  sure  to  result.  So 
to  cause  infection  bacteria  must  enter  the  body  through 
channels  best  adapted  to  their  growth  and  multi- 
plication. 

Concerning  the  individual  exposed  to  infection  it  °^Ttilaft 
is  known  that  everyone  is  endowed  to  a  variable  de- 
gree  with  defensive  substances  in  -the  blood  and 
tissues  that  tend  to  overcome  and  destroy  invading 
bacteria.  Unhealthy  people,  as  everyone  knows,  are 
more  likely  to  become  infected  and  to  succumb  to  in- 
fection than  the  healthy.  This  power  of  the  human 


32  BACTERIOLOGY. 

organism  to  resist  infection  will  be  discussed  more 
fully  under  the  subject  of  immunity. 

How  does  infection  take  place?  It  is  the  result  of 
the  invasion  of  the  body  tissues  by  pathogenic  bacteria 
that  live  either  on  the  surface  of  the  body  or  from 
those  that  live  on  the  mucous  membranes  inside  the 

Infec- 

tion  from    body.      Injuries  play   an   important  part   in  causing 
outside     infections.     Injuries  caused  by  firearms  may  be  the 

the  body  J  •[  J 

entering  point  of  tetanus  bacilli,  the  cause  of  lockjaw, 
while  rabies  or  hydrophobia  is  spread  through  the  bites 
of  mad  dogs.  Careless  manipulations  with  soiled 
catheters,  speculums,  syringes,  and  so  on  may  cause 
injury  to  the  tissues  and  be  the  means  of  introducing 
bacteria.  In  the  case  of  the  contagious  fevers  like 
measles,  chicken-pox,  whooping-cough,  and  scarlet 
fever  the  infecting  agent  seems  to  be  in  the  air  and 
causes  infection  by  being  inhaled.  Bedding,  clothing, 
and  utensils  that  have  been  contaminated  with  infec- 
tious material  may  be  the  means  of  spreading  infec- 
tion. Finally,  the  bites  of  insects  and  vermin  may 
cause  infection.  It  is  known  that  certain  kinds  o<f 
mosquitoes  transmit  malarial  fever  and  yellow  fever; 
flies  may  spread  typhoid  fever  by  depositing  the 
typhoid  bacilli  on  food  materials. 

tio£ffrom  The  bo^y  may  ke  looked  upon  as  the  host  for 

bfivtinga     large  numbers  of  bacteria.      At  birth,   however,   all 

thesbody    healthy  animals  are  free  from  bacteria;  but  almost 

immediately  afterward  they  are   deposited   upon  the 

surface  of  the  body  by  the  dust  in  the  air,  and  are 

introduced   into   the  body  by   food   and   by  the   air 


INFECTION  AND  IMMUNITY.  33 

breathed.  When  these  bacteria  gain  access  to  the 
body,  only  those  survive  that  find  the  conditions  favor- 
able for  their  existence.  For  this  reason  it  is  found 
that  each  cavity  o-r  portion  of  the  body  harbors  a 
group  of  bacteria  peculiar  to  it.  The  varieties  of  bac- 
teria found  in  the  saliva,  for  example,  are  quite  dif- 
ferent from,  those  found  in  the  intestine.  Most  of 
these  constant  bacteria  of  the  body  are  harmless,  but 
some  pathogenic  forms  occur  which  manifest  their 
power  to  produce  disease  only  when  some  injury 
affords  a  point  of  entrance  to  the  tissues  or  the  re- 
sistance of  the  individual  is  lowered.  Thus  in  the 
skin  there  may  be  many  kinds  of  bacteria,  the  most 
important  of  which  are  the  pus-forming  cocci,  the 
staphylococci,  and  streptococci.  They  do>  no  harm 
under  normal  conditions,  but  if  there  is  any  injury 
to  the  skin  these  organisms  may  enter  and  give  rise  to 
a  boil,  an  abscess,  or  erysipelas.  It  is  mainly  against 
these  pus-forming  bacteria  that  the  preparation  of  the 
patient  before  operation  is  directed.  Unfortunately 
these  bacteria  live  actually  in  the  skin,  that  is,  below 
the  surface;  so  that  skin  disinfection  must  be  very 
thorough  to  be  effectual  and,  even  under  most  favor- 
able conditions,  cannot  be  considered  as  absolute. 

In  the  air-passages  large  numbers  of  bacteria  are 
found  which  enter  with  the  air  breathed  in.  Most  of 
them  are  caught  on  the  moist  surfaces  of  the  mouth, 
throat,  and  nose ;  very  few  if  any  ever  reach  the  lungs 
directly  through  the  trachea  and  bronchi.  In  the 
mouth  the  pneumococci,  staphylococci,  and  strepto- 


34  BACTERIOLOGY. 

cocci  are  frequently  present,  but  do  no  harm  unless  the 
vitality  is  lowered.  The  stomach  is  generally  free 
from,  bacteria,  due  to  the  acid  in  its  secretions.  If 
however  there  is  any  disturbance  of  digestion  and  the 
secretions  are  no  longer  acid,  the  bacteria  swallowed 
in  the  food  may  cause  fermentation  and  other  dis- 
orders. The  intestine  harbors  great  numbers  of  bac- 
teria, chiefly  the  colon  bacillus*  and  others  closely 
allied  to  it.  They  are,  in  health,  not  only  harmless, 
but  of  much  benefit  in  breaking  down  the  food  into 
substances  that  can  be  absorbed  for  nutriment  of  the 
tissues.  Under  conditions  of  lowered  resistance  or 
when  injury  to  the  intestines  has  been  done,  they  may 
cause  infection. 

After  infection  has  taken  place  it  may  remain 
localized  in  the  form  of  a  boil  or  abscess,  or  it  may 
spread  so  that  the  blood  contains  the  infecting  organ- 
ism. When  infections  become  generalized  the  condi- 
tion is  called  septicemia,  and  when  there  is  added  to 
this  scattered  areas  of  pus  formation  throughout  the 
body  the  condition  is  called  pyemia.  Toxemia  is  the 
condition  caused  by  the  poisons  of  bacteria,  either  in 
local  or  general  infections. 

How  do  bacteria  produce  injury  to  the  tissues? 
In  two  ways:  The  multiplication  of  bacteria  in  the 
tissues  may  cause  injury  in  a  mechanical  way  by 
obstructing  the  very  small  blood-vessels,  causing  the 
necrosis  or  death  of  the  tissue.  The  absorption  of  the 
necrotic  material  gives  rise  to  the  symptoms  of  infec- 
tion. Much  greater  injury  is  produced  by  the  absorp- 


INFECTION  AND  IMMUNITY.  35 

tion  of  the  poisons  or  toxins  made  by  the  bacteria. 
These  poisons  may  be  extracellular  or  intracellular. 
The  extracellular  toxins  are  thrown  out  of  the  bodies  Toxins 

extra-  and 


of  the  bacteria  into  the  tissues  or  media  in  which  they 
are  growing.  The  word  toxin  when  used  alone  is 
taken  to  mean  an  extracellular  toxin.  The  intracel- 
lular or  endotoxins  are  retained  within  the  bodies  of 
the  bacteria  and  are  set  free  only  after  their  death  or 
dissolution.  After  absorption  the  bacterial  toxins  do 
not  affect  all  organs  or  tissues  equally,  but  exhibit  a 
selective  action,  some  attacking  the  red  blood-cor- 
puscles and  dissolving  them,  others  the  tissues  of  the 
brain  and  nervous  system. 

One  might  think,  from  what  has  been  said,  that  immunity 
men  and  animals  are  wholly  at  the  mercy  of  bacteria. 
Fortunately  this  is  not  so,  as  all  are  endowed  with 
certain  defensive  powers  that  resist  the  injurious 
action  of  bacteria  and  their  poisons.  This  resistance 
to  disease  is  called  immunity. 

Many  of  the  diseases  that  are  infectious  in  man 
cannot  be  transmitted  to  animals  and,  conversely,  some 
of  the  infectious  diseases  of  animals  do  not  occur  in 
man. 

Among  the  races  of  men  variations  in  the  resist- 
ance to  disease  is  observed;  for  example,  the  negro 
seems  to  possess  a  much  greater  resistance  to  infection 
with  yellow  fever  than  the  white  man.  In  addition  to 
the  variations  in  resistance  among  the  races  of  man 
there  are  also  variations  among  individuals.  The 
conditions  under  which  people  live  have  much  to  do 


36 


BACTERIOLOGY. 


Racial 
immunity 


Acquired 
immunity 


with  their  resistance.  Unsanitary  homes  and  work- 
shops, fatigue,  exposure,  poor  nourishment,  and  in- 
juries all  tend  to  lower  the  resistance  to  disease.  The 
excessive  or  continued  use  of  alcohol  is  a  very  im- 
portant factor  in  lowering1  resistance,  as  is  shown  by 
the  frequency  of  infectious  disease,  particularly  pneu- 
monia and  tuberculosis,  among  drinkers.  Constitu- 
tional diseases  like  diabetes  and  nephritis  also>  lower 
the  resistance. 

It  is  possible  to  acquire  immunity.  Following  an 
attack  of  infectious  disease  there  commonly  results  an 
immunity  that  protects  the  individual  from  a  second 
attack.  The  resistance  gained  in  this  way  is  spoken 
of  as  acquired  immunity  and  follows  diseases  such  as 
measles,  mumps,  scarlet  fever,  and  typhoid  fever.  The 
duration  of  acquired  immunity  varies;  after  scarlet 
fever  it  oftentimes  lasts  during  life,  while  after  typhoid 
fever  it  may  last  only  a  year  or  two.  That  immunity 
could  be  acquired  in  this  way  was  known  many  years 
ago,  and  led  to  the  conception  of  producing  immunity 
artificially  without  actually  causing  the  individual  to 
pass  through  the  dangers  of  disease.  Although  not 
the  first  to  attempt  to  produce  immunity  artificially, 
the  experiments  of  Jenner,  who  discovered  the  pro- 
tective effects  of  vaccination,  were  the  most  success- 
ful. The  events  leading  up  to  Jenner's  discovery  are 
interesting.  In  England,  where  smallpox  had  been  a 
scourge  for  many  years,  it  was  observed  that  people 
who  had  been  accidentally  infected  with  cow-pox,  a 
modified  form  of  smallpox  in  cattle,  were  not  attacked 


INFECTION  AND  IMMUNITY.  37 

by  smallpox  even  though  they  were  exposed  to  it. 
Jenner  reasoned  that  if  an  accidental  infection  with 
cow-pox  could  prevent  against  smallpox  it  would  be  a 
rational  procedure  to  purposely  infect  with  cow-pox. 
So,  acting  on  the  advice  of  his  patron,  Dr.  John 
Hunter,  he  inoculated  a  boy  with  pus  from  a  cow-pox 
pustule  in  May,  1796,  and  two  months  later  injected 
the  pus  from  a  smallpox  pustule  without  producing 
any  disease. 

When  immunity  is  acquired  by  introducing  into 
the  body  the  infectious  agents  in  modified  form  or  in 
small  amount,  it  is  spoken  of  as  active  immunity  be- 
cause the  body  tissues  take  an  active  part  in  forming 
the  substances  that  give  protection.  Our  knowledge 
of  how  immunity  is  produced  in  this  way  is  due  prin- 
cipally to  Pasteur,  who'  found  that  the  bacteria  pro- 
ducing cholera  among  fowls  became  much  less  virulent 
after  being  cultivated  for  long  periods  of  time  on 
artificial  culture  media  or  after  cultivation  at  increased 
temperatures.  By  injecting  gradually  increasing 
amounts  of  these  attenuated  bacteria  of  chicken- 
cholera  into  fowls  he  was  able  to  immunize  them  to 
the  disease. 

The  introduction  of  dead  bacteria  or  vaccines  in  vaccines 
increasing  doses  is  often  used  to  develop  immunity 
against  those  bacteria  whose  poisons  are  intracellular. 
This  method  has  been  practised  a  great  deal  these  last 
few  years,  and  has  been  attended  with  considerable 
success  in  some  infections.  Its  most  successful  appli- 


38  BACTERIOLOGY. 

cation  has  been  in  the  preventive  inoculation  against 
typhoid  fever  in  the  army. 

immunity  There  is  another  type  of  immunity  that  can  be 

conferred  without  the  body  tissues  taking  any  active 
part  in  the  process.  For  this  reason  it  is  called  passive 
immunity.  In  1890  von  Behring  discovered  that  the 
blood-serum  of  animals  that  had  been  immunized  to 
the  poisons  of  diphtheria  and  tetanus,  if  injected  into 
other  animals,  would  protect  them  also.  Quite  re- 
cently Dr.  Flexner,  at  the  Rockefeller  Institute  in  New 
York,  made  similar  observations  in  connection  with 
the  poison  of  the  meningococcus,  the  organism  caus- 
ing the  epidemic  form  of  cerebrospinal  meningitis. 

Perhaps  a  brief  description  of  the  way  diph- 
theria antitoxin  is  made  will  make  this  type  of  im- 
munity better  understoood.  The  animal  used  in  the 
commercial  preparation  of  diphtheria  antitoxin  is  the 
horse.  At  the  start  the  animal  is  inoculated  with  a 
very  small  dose  of  the  diphtheria  toxin  obtained  by 
growing  the  diphtheria  bacillus  on  large  flasks  of 
bouillon.  The  bacilli  are  filtered  out  and  the  filtrate 
containing  the  soluble  diphtheria  toxin  is  used  for 
injecting.  The  effect  of  the  first  injection  is  to  make 
the  horse  sick,  but  not  fatally  so.  At  the  end  of  a 
week  a  second  injection  is  made  with  the  same  dose, 
but  the  animal  is  now  able  to  stand  the  poison  without 
ill  effect.  Each  week  the  dose  is  increased  until  at  the 
end  of  two  or  three  months  the  animal  is  able  toi  with- 
stand enormous  doses  of  the  poison  without  ill  effect, 
due  to  the  protective  substances  formed  in  its  body. 


INFECTION  AND  IMMUNITY.  39 

In  other  words,  active  immunity  has  been  established, 
in  the  horse.  At  the  end  of  three  or  four  months  the 
animal  is  bled  to  the  amount  of  five  or  six  quarts,  and 
the  blood  is  set  aside  to  clot.  In  the  serum  that  sep- 
arates from  the  clot  are  the  same  substances  that  pro- 
tected the  horse  from  the  diphtheria  poison.  This  is 
the  diphtheria  antitoxin.  It  is  standardized  by  de- 
termining the  smallest  amount  of  antitoxin  that  will 
neutralize  100  times  the  fatal  dose  of  toxin  for  a 
guinea-pig  weighing  250  grams.  This  amount  is 
called  the  antitoxin  unit,  and  enables  us  to  measure 
the  dose  of  antitoxin. 

What  the  nature  of  these  substances  is  that  en- 
ables us  to  resist  infection  is  not  known,  and  the  way 
in  which  they  act  is  built  up  on  theory  that  is  com- 
plicated and  difficult  to  understand.  It  is  sufficient  for 
us  to  know  that  soon  after  infection  occurs  the  body 
tissues  and  fluids  begin  to  protect  themselves  against 
the  invading  bacteria  and  their  poisons.  The  first 
defense  is  made  by  the  white  blood-corpuscles,  or 
leucocytes,  the  scavenger  cells  of  the  blood.  They 
are  attracted  in  great  number  to>  the  point  of  infection 
and  destroy  the  invading  bacteria  by  taking  them  into 
their  cell  bodies  and  digesting  them.  The  fate  of 
infections  depends  many  times  on  the  defense  of  the 
phagocytes;  if  they  are  sufficient  for  the  needs  of  the  Phago- 
occasioii,  the  infection  is  checked  and  localized ;  if  they 
are  not,  the  infection  extends  and  may  become  general. 

The  body,  however,  does  not  rely  entirely  on  the 
phagocytes  for  protection.     Infection  stimulates  the 


40  BACTERIOLOGY. 

Bacterio-  tissues  to  form  substances,  circulating  in  the  blood- 
serum,  which  combine  with  and  neutralize  the  poisons 
of  bacteria.  They  are  spoken  of  as  antibodies  and  act 
in  different  ways;  some,  called  bacteriolysins,  dis- 

"tSfnUs~  s°lve  tne  bacterial  cells ;  others  gather  the  bacteria  into 
clumps  or  clusters;  these  are  called  agglutinins;  and 
finally  substances  may  be  formed  that  act  on  the  bac- 
teria in  such  a  way  as  toi  make  them  more  readily 

opsonins    digested  by  the  phagocytes;  these  are  called  opsonins. 

It  is  an  interesting  fact,  and  one  of;  much  impor- 
tance, that  the  amount  of  these  protective  substances 
formed  is  not  only  sufficient  to1  render  an  infection 
harmless,  but  is  greatly  in  excess  of  the  needs  of  the 
moment.  They  remain  stored  away  in  the  tissues 
ready  to  be  utilized  when  the  same  infective  agent 
again  attacks;  this  is  the  way  that  immunity  is 
•  established. 

The  word  anaphylaxis,  literally  translated  from 
the  Greek,  means  against  protection,  the  exact  op- 
posite of  prophylaxis,  which  means  for  protection. 
This  name  has  been  given  to  a  condition  of  hypersen- 
sitiveness  which  has  been  found  to  exist  in  certain 
animals  and  man.  For  example,  it  has  been  shown 
that  guinea-pigs  may  be  made  sensitive  to  harmless 
proteids  like  egg-albumin  or  milk.  The  first  injec- 
tion causes  no  symptoms,  but  the  second,  even  when 
the  dose  is  smaller,  may  cause  shortness  of  breath, 
spasms,  and  death.  It  requires  from:  ten  to  fourteen 
days  after  the  first  injection  for  this  hypersensitiveness 
to  develop. 


INFECTION  AND  IMMUNITY.  41 

A  similar  hypersensitiveness  has  been  observed  in 
some  human  beings  to  the  horse  serum  in  diphtheria 
antitoxin,  and  the  symptoms  of  serum  sickness  have 
been  attributed  to  it  (see  Diphtheria).  The  reactions 
following  the  use  of  tuberculin  and  mallein  are  also 
believed  to  be  due  to  anaphylaxis. 


CHAPTER  V. 
THE  GROUP  OF  PYOGENIC  COCCI. 

IN  the  following  chapters  the  characteristics  of 
the  individual  species  of  bacteria  associated  with  the 
production  of  disease  will  be  considered.  Inasmuch 
as  certain  ones  are  closely  related  in  their  growth,  mor- 
phology, and  manner  of  producing  infection,  it  is  con- 
venient to  form  them-  into  groups;  thus  there  is  the 
group  of  pyogenic  cocci  (pus-forming  cocci)  and  the 
intestinal  group,  which  may  also  be  subdivided  into 
the  typhoid  and  dysentery  groups.  On  account  of 
their  wide  distribution  and  the  frequency  with  which 
they  cause  infection,  the  pyogenic  group  will  be  con- 
sidered first, 
staphyio-  The  coccus  that  most  commonly  causes  infection 

coccus        .  . 

pyogenes  is  the  staphylococcus,  so  named  because  of  its  charac- 
teristic arrangement  into  clusters  often  likened  to 
bunches  of  grapes.  (See  Fig.  i,  A,  page  7.)  Several 
varieties  are  distinguished  by  the  pigment  they  pro- 
duce when  grown  in  cultures.  The  Staphylococus 
aureus  produces  a  golden-yellow  pigment,  the  S. 
citreus  a  lemon-yellow  pigment,  while  the  S.  albus 
grows  without  forming  any  color.  The  Staphylococcus 
epidermictis  albus  is  a  variety  found  in  the  under  layers 
of  the  skin.  The  size  of  these  coccus  forms  differ, 
some  being  larger  than  others.  They  do  not  form 
spores,  and  all  are  without  motility. 
(42) 


GROUP  OF  PYOGENIC  COCCI.  43 

The  aureus  is  the  most  virulent  of  all  staphylo- 
cocci.  The  infections  caused  by  the  staphylococci  vary 
with  the  virulence  of  the  organism;  and  the  resistance 
of  the  individual  infected.  The  infection  may  be  local 
like  a  boil  or  an  abscess,  or  it  may  extend  to  involve 
large  areas  of  tissue  (cellulitis). 

General  infections,  septicemia,  and  pyemia  are 
very  often  caused  by  these  organisms.  Malignant 
endocarditis  and  puerperal  fever  come  under  this  head. 
They  are  usually  the  cause  of  infection  in  wounds, 
although  there  are  other  bacteria  that  may  do  this.  It 
is  to  remove  all  bacteria,  especially  the  pus-cocci 
coming  in  contact  with  the  patient,  that  the  precau- 
tions or  technique  of  the  operating-room  is  directed. 
Since  the  pus-cocci  are  so  often  found  on  the  skin, 
careful  washing  and  scrubbing  of  the  hands  followed 
by  a  disinfectant  is  employed  to  destroy  them.  It  is 
important  to  remember  that  these  precautions  cannot 
be  safely  performed  in  a  careless  manner,  as  the  pyo- 
genic  cocci  may  be  located  in  rather  than  on  the  skin. 
They  are  to  some  degree  resistant  to*  disinfectants,  and 
require  an  exposure  of  at  least  ten  minutes  in  a  i :  1000 
solution  of  bichloride  of  mercury. 

The  injury  caused  in  infections  by  the  staphy- 
lococci is  duo  almost  wholly  to  the  toxins  in  part  set 
free  and  in  part  retained  in  their  cell  bodies,  and 
liberated  in  the  dissolution  after  death.  The  toxins 
cause  the  formation  of  pus  and  also'  attack  the  red 
blood-cells,  dissolving  them.  This  explains  the  anemia 
that  always  accompanies  these  infections. 


44  BACTERIOLOGY, 

strepto-  The  streptococcus  is  one  of  the  pus-forming  cocci 

COCCUS  I  •  1  •  • 

pyogenes  that  is  characterized  by  multiplication  in  one  plane, 
producing  strings  or  chains  of  cocci.  (See  Fig.  i,  A, 
3,  page  7.)  There  are  numerous  varieties  of  strepto- 
cocci that  differ  in  size,  shape,  and  virulence.  They 
may  be  found  in  water,  milk,  dust,  and  discharges 
from  the  intestinal  tract.  In  general  they  are  more  re- 
sistant to  harmful  influences  than  the  staphylococci, 
and  more  virulent ;  consequently  infections  due  to  them 
are  more  serious  and  attended  with  a  higher  mor- 
tality rate.  The  toxic  symptoms,  fever,  rigors,  sweats, 
and  so  o>n,  are  more  pronounced. 

Infections  with  the  streptococcus  may  be  localized 
as  in  the  case  of  boils,  abscesses,  and  carbuncles;  but 
because  of  the  greater  virulence,  they  are  liable  to 
cause  edema  and  to  extend  along  the  lymphatic  vessels 
to  involve  the  adjacent  lymphatic  glands.  In  the  lungs 
the  streptococcus  frequently  causes  pneumonia  and 
empyema;  in  the  throat,  tonsillitis  with  the  formation 
of  a  membrane  often  identical  with  that  seen  in  diph- 
theria, and,  in  the  skin,  erysipelas.  It  is  often  the 
infecting  agent  in  disease  of  the  bones,  osteomyelitis, 
and  in  the  general  infections  such  as  endocarditis  and 
puerperal  fever.  In  association  with  other  bacteria 
they  gave  rise  to  what  are  called  mixed  infections, 
coccus  The  Micrococcus  tetragcnus  is  a  pus-forming 

tetnufe"  organism  of  low-grade  virulence.  Its  arrangement  is 
peculiar,  forming  squares  of  four  cocci.  It  is  found 
frequently  in  the  sputum  and  causes  infection  usually 
in  combination  with  some  other  micro-organism. 


GROUP  OF  PYOGENIC  COCCI. 


45 


The  gonococcus  is  the  organism,  causing  gonor-  The  gono- 

,.  ...  coccus 

rhea.  It  is  a  diplococcus,  always  occurring  in  pairs 
with  the  surfaces  facing  one  another  flattened  like  two 
coffee-beans.  In  pus  it  is  found  almost  always  within 
the  bodies  o>f  the  leucocytes.  It  is  very  difficult  to 


Fig.  4. — Gonorrhea!  pus,  showing  gonococci  within  a  leucocyte. 

cultivate,  as  it  does  not  grow  on  the  ordinary  culture 
media.  By  the  diplococcus  form,  coffee-bean  shape, 
and  situation  within  the  leucocytes,  it  is  identified  by 
direct  microscopic  examination  of  pus. 

Infection  with  the  gonococcus,  or  gonorrhea,  is 
classed  as  a  venereal  disease  because  it  is  commonly 
confined  to  the  genital  organs.  It  is  an  exceedingly 
common  disease,  and  is  spread  almost  always  by 


46  BACTERIOLOGY. 

sexual  contact.  In  the  male  the  infection  starts, 
after  an  incubation  period  of  five  to  seven  days,  with 
a  discharge  of  pus  from  the  urethra.  The  acute 
stage  lasts  usually  from  three  to  six  weeks,  and  then 
recedes  either  entirely  or  leaves  a  catarrhal  inflam- 
mation which  may  last  and  be  infectious  for  an  in- 
definite period.  In  approximately  half  of  the  cases, 
however,  the  infection  extends  back  to  involve  the 
bladder,  prostate  gland,  or  seminal  vesicles.  When 
this  happens  the  gonococci  become  buried  in  the  tis- 
sues and  frequently  remain  dormant  for  years,  only 
to  light  up  again  when  conditions  favor  it.  Infection 
of  these  organs  is  most  difficult  to-  eradicate,  and  a 
person  so  infected  may  be  able  to-  transmit  the  disease 
to  others  over  long  periods  of  time.  It  is  a  frequent 
cause  of  sterility  in  the  male. 

In  the  female  the  infection  likewise  starts  in  the 
urethra,  but  very  soon  spreads  to-  the  glands  of  Bar- 
tholin  situated  beneath  the  floor  of  the  vagina. 
Later  it  may  extend  to  the  cervix  of  the  uterus, 
thence  to  the  mucous  lining,  to  involve  finally  the 
Fallopian  tubes.  It  has  been  recognized  for  years 
that  gonorrhea!  infections  are  responsible  for  the 
great  majority  of  inflammations  of  the  uterus  and 
Fallopian  tubes  that  require  surgical  intervention.  The 
disease  is  harder  to  combat  in  the  female  than  in  the 
male,  partly  because  the  acute  symptoms  are  not  so 
marked,  and  so  the  nature  of  the  infection  may  escape 
detection,  and  partly  because  the  anatomy  of  the 
organs  infected  is  such  that  it  is  next  to*  impossible  to 


GROUP  OF  PYOGENIC  COCCI.  47 

treat  the  infection  thoroughly.  The  period  over  which 
the  disease  may  continue  infectious  in  the  female  may 
be  years,  and  if  the  tubes  and  ovaries  are  involved 
sterility  usually  ensues. 

Gonorrhea!  infection  of  the  eyes  is  fairly  com- 
mon.  It  occurs  in  the  newborn  most  often,  and  is 
called  ophthalmia  neonatorum.  Ulcers  on  the  cornea 
which  interfere  with  vision  in  later  life,  or  complete 
destruction  of  the  eyeball,  may  result.  It  is  the  chief 
cause  of  blindness  in  children.  The  infection  gets 
into  the  eyes  during  delivery,  and  as  a,  prophylactic 
measure  it  is  advisable  to  instil  a  drop  or  two>  of  i 
per  cent,  nitrate  of  silver  into  the  eyes  immediately 
after  birth.  In  adults  the  infection  is  usually  intro- 
duced by  infected  fingers,  handkerchiefs,  or  towels. 

Among  children  in  institutions  gonorrheal  infec-  Vaeinitis 
tion  o>f  the  vagina,  vaginitis,  occurs  in  epidemic  form. 
It  spreads  from  child  to  child  with  great  rapidity, 
and  is  very  difficult  to  check.  The  infection  starts 
from  one  child  so  infected,  and  is  spread  by  napkins, 
towels,  or  directly  from  one  child  to  another. 

While  infections  with  the  gonococcus  are  gen- 
erally localized,  they  may  in  rare  instances  become 
general,  causing  arthritis,  endocarditis,  and  menin- 
gitis. The  toxin  of  the  gonococcus  is  within  the 
body  of  the  organism,  and  is  liberated  only  after 
death  of  the  cell  body.  Dead  cultures,  of  gonococci, 
or  vaccines,  have  been  employed  in  the  treatment  of 
the  infection,  but  have  proven  only  partially  success- 
ful in  the  complications  such  as  arthritis,  epididymitis, 


48  BACTERIOLOGY. 

orchitis,  and  the  vaginitis  of  children.  Serum  ob- 
tained from  animals  that  have  been  immunized  with 
living  cultures  of  gonococci  (active  immunization) 
has  also  been  only  partly  successful,  probably  because 
there  seems  to  be  a  great  many  different  strains  or 
families  of  gonococci. 
The  pneu-  Pneumonia  is  an  acute  infectious  disease  caused 

mococcus  .  .  . 

by  a  variety  of  micro-organisms,  the  chief  one  being 
the  Diplococcus  pneumonia,  or  the  pneumococcus. 
Other  bacteria,  such  as  the  streptococcus,  staphylo- 
coccus,  the  influenza  and  typhoid  bacillus,  may  also 
cause  pneumonia. 

The  pneumococcus  is  a  small,  lance-shaped  organ- 


ism, usually  arranged  in  pairs,  and  these  pairs  may 
form  chains  not  unlike  the  streptococcus  in  appear- 
ance. About  each  pair  there  may  be  seen  in  suitable 
preparations  a  capsule  with  a  clear  zone  between  it 
and  the  body  of  the  organism.  The  capsule  is  seen 
best  in  smears  of  the  fresh  sputum  from  pneumonia 
patients,  and  is  of  considerable  importance  in  identify- 
ing the  organism. 

Pneumococci  are  present  in  the  mouth  and  throat 
of  most  persons  in  health,  and  cause  no  injury  or 
infection  unless  the  resistance  of  the  individual  is 
lowered.  Some  of  the  factors  that  lower  the  re- 
sistance are:  exposure,  alcoholism,  debilitating  and 
wasting  diseases,  unhealthy  surroundings,  and  other 
infectious  diseases,  particularly  scarlet  fever  and 
measles.  When  the  resistance  has  been  lowered  the 
pneumococci  in  the  mouth  or  throat  may  gain  en- 


GROUP  OF  PYOGENIC  COCCI. 


49 


trance  to  the  lungs  -by  way  of  the  circulating  blood. 
Infection  of  the  lungs  by  direct  invasion  through  the 
respiratory  tract  is  improbable.  The  popular  idea 
that  pneumonia  is  the  direct  result  of  taking  cold  is 


Fig.  5. — Diplococcus  pneumonise  in  the  heart's  blood  of  a  rabbit. 
X   1000.     (After  Frankel-Pfeiffer.) 

erroneous.  While  it  is  true  that  exposure  to  cold 
may  so  lower  the  resistance  as  to  favor  the  infection 
of  the  lungs,  pneumonia  rarely  follows  a  simple  cold. 
The  infection  in  pneumonia  is  general,  that  is,  a  sep- 
ticemia  in  which  the  manifestations  are  localized 


50  BACTERIOLOGY. 

chiefly  in  the  lungs.  With  this  conception  of  the 
disease  in  mind,  it  js  easy  to*  understand  how  the 
complications  such  as  otitis  media  (a  suppuration  of 
the  middle  ear)  and  meningitis  may  occur. 

That  pneumonia  may  be  communicated  from 
one  person  to  another  is  proved!  by  the  outbreaks  of 
the  disease  in  epidemic  form  in  crowded  buildings 
such  as  barracks  and  hospitals.  It  is  not  spread  by 
direct  contact,  however,  as  frequently  as  are  many  of 
the  other  infectious  diseases.  During  the  course  of 
pneumonia  the  pneumococcus  is  present  in  large 
numbers  in  the  sputum  and,  as  the  pneumonic  sputum 
is  usually  tenacious  and  difficult  to  expel,  the  hands 
and  bed-linen  are  frequently  contaminated  by  it.  By 
coughing  and  sneezing  the  virus  may  be  scattered 
about  the  sickroom  and  hospital  ward,  and  in  this 
precau-  way  become  a  part  of  the  dust.  Precautions  therefore 
should  be  taken  to  collect  all  sputum  in  paper*  boxes 
or  napkins  and  to  burn  it.  The  hands  of  the  patient 
should  be  kept  clean  with  disinfectant  (bichloride  of 
mercury  i :  1000),  and  any  contamination  of  the 
clothing  should  be  disinfected  promptly.  It  is  ad- 
visable for  attendants  on  pneumonia  patients  to  dis- 
infect the  hands  after  handling  the  patient.  Rooms 
and  apartments  that  have  been  occupied  by  pneu- 
monia patients  should  be  disinfected  at  the  termina- 
tion of  the  illness. 

Cerebrospinal  meningitis  is  an  infectious  disease 
in  which  the  agent  of  infection  produces  an  inflamma- 
tion of  the  covering  of  the  brain  and  spinal  cord. 


GROUP  OF  PYOGENIC  COCCI.  51 

The  infection  may  be  caused  by  any  one  of  a  number    The  Me 
of  micro-organisms, — the  pneumococcus,  the  typhoid      coccus 
bacillus,   the   influenza  bacillus,   the  tubercle  bacillus, 
the  Streptococcus  or  Staphylococcus  pyogenes.    When 
the    meningitis    results    from    infection    with    these 
organisms  it   is  generally  secondary  to  an   infection 
elsewhere  in  the  body,  as,  for  example,  during  pneu- 
monia,   typhoid    fever,    pulmonary    tuberculosis,    or 
septicemia. 

The  primary  form  of  meningitis,  the  form  that 
frequently  occurs  in  epidemics  and  is  more  commonly 
called  spotted  fever,  is  due  to  infection  with  the 
meningococcus  or  the  Micrococcus  intracellularis 
menmgitidis,  and  must  not  be  confused  with  the  forms 
mentioned  above,  which  are  always  secondary. 

The  meningococcus  was  identified  and  described 
by  Professor  Weichselbaum  in  1887.  The  micro- 
organism was  found  in  the  cerebrospinal  fluid  of 
patients  sick  with  the  disease,  and  generally  within  the 
bodies  of  the  leucocytes.  For  this  reason  the  term 
intracellular  is  used  in  its  description.  The  coccus 
occurs  in  pairs,  a  diplococcus  which  in  appearance  is 
not  unlike  the  gonococcus.  It  can  be  cultivated  on 
the  ordinary  laboratory  media. 

The  presence  of  the  disease  is  detected  by  finding 
the  meningococcus  in  the  cerebrospinal  fluid,  which  is 
withdrawn  by  inserting  an  aspirating  needle  into  the 
cerebrospinal  canal,  at  the  level  of  the  third  or  fourth 
lumbar  vertebra.  This  procedure  is  spoken  of  as 
lumbar  puncture,  and  may  be  performed  by  physi- 


Morphol- 
ogy 


52  BACTERIOLOGY. 

cians  without  danger  to  the  patient.  The  fluid  re- 
covered in  this  manner  is  received  into*  sterile  test- 
tubes,  and  immediately  centrifuged  to  throw  down 
the  cellular  elements  contained,  in  it.  After  this  has 
been  done  the  deposit  is  spread  thinly  on  slides,  ap- 
propriately stained,  and  examined  under  the  micro- 
scope. The  meningococcus  when  present  is  identified 
by  its  shape  and  arrangement  in  pairs,  and  by  its 
location  within  the  bodies  of  the  leucocytes.  The 
macro-organism  may  be  cultivated  from  the  spinal 
fluid.  In  addition  to  its  use  as  a  diagnostic  aid,  lum- 
bar puncture  is  very  often  the  means  of  relieving  the 
symptoms  of  pressure  due  to  an  excessive  amount 
of  fluid  in  the  spinal  canal,  and  for  this  reason  it  is 
customary  to  remove  a  large  amount  of  the  fluid. 

The  meningococcus  is  spread  by  the  discharges 
from  the  mouth,  nose,  and  ears  of  patients  sick  with 
meningitis,  and  it  is  not  infrequent  to  find  the  organ- 
isms in  the  secretions  of  the  nose  and  mouth  of  those 
attending  them.  Occasionally  they  may  be  found  in 
the  nasal  secretions  of  healthy  people  who  may  act  as 
preven-  carriers  of  the  infection.  To  prevent  the  disease  from 
spreading  it  is  essential  first  of  all  to  remove  the 
patient  from  contact  with  others,  especially  during  the 
first  two  weeks  of  the  disease,  for  at  this  period  the 
infection  is  most  virulent.  Then  all  discharges  from 
the  mouth,  nose,  eyes,  and  ears  should  be  collected  on 
cloths  and  paper  napkins  and  burned.  Nurses  in 
attendance  should  use  great  care  to  disinfect  the 
hands  after  handling  the  patient,  and  spray  the  nose 


GROUP  OF  PYOGENIC  COCCI.  53 

and  mouth  with  antiseptic  solutions.  Children  living 
in  the  samei  house  should  not  be  permitted  to  attend 
school  until  it  is  certain  that  they  have  not  been 
infected. 

Cerebrospinal  meningitis  in  the  epidemic  form 
has  been  attended  with  a  very  high  mortality  in  the 
past,  especially  among  young  children.  In  some  epi- 
demics it  has  been  as  high  as  90  per  cent.  The  treat- 
ment  with  antimeningitis  serum,  however,  has  been 
attended  with  success,  and  the  excessive  mortality  has 
been  considerably  reduced  by  its  use.  In  this  country 
this  method  of  treatment  was  begun  by  Dr.  Flexner 
and  Dr.  Jobling  at  the  Rockefeller  Institute  in  New 
York.  The  serum,  is  made  by  injecting  horses  with 
slowly  increasing  doses  of  meningococci  that  have 
been  killed  by  heat.  The  tolerance  of  the  animals  to 
the  poison  of  the  meningococci  is  gradually  increased 
in  this  way  until  they  are  able  to  withstand  many 
times  the  fatal  dose.  This  tolerance  depends  upon  an 
active  immunity  due  to  the  formation  within  their 
bodies  of  protective  substances  that  neutralize  the 
poison.  After  eight  or  twelve  months  the  horses  are 
bled  and  the  blood-serum  containing  the  protective 
substances  is  used  for  treating  patients  sick  with 
meningitis. 

The  extended  trial  of  the  serum  in  a  number  of 
epidemics  has  shown  that,  the  earlier  it  is  used  after 
the  onset  of  the  infection,  the  greater  its  curative 
value.  For  this  reason  it  is  customary  to'  inject  the 
serum  immediately  after  the  withdrawal  of  the  cere- 


54  BACTERIOLOGY. 

brospinal  fluid  by  lumbar  puncture,  without  waiting 
to  determine  the  nature  of  the  infecting  organism. 
Subsequent  injections  are  controlled  by  the  presence 
or  absence  of  the  meningococcus  in  the  cerebrospinal 
fluid. 


CHAPTER  VI. 

THE  BACILLI  OF  THE  COLON,  TYPHOID, 
DYSENTERY  GROUP. 

THESE  organisms  are  usually  grouped  together 
because  of  the  similarity  in  their  appearance  and 
manner  of  growth  upon  artificial  culture  media.  All 
the  members  of  this  group  are  short,  rod-shaped,  often 
forming  chains,  but  never  forming  spores.  They  are 
all  motile. 

Under  the  name  of  colon  bacilli  are  grouped  a 
number  of  varieties  very  closely  related,  which  are  bacillus 
usually  harmless  parasites  living  in  the  bodies  of  man 
and  animals,  but  which  at  times  become  pathogenic 
and  cause  infection.  The  colon  bacillus  itself,  prop- 
erly called  the  Bacillus  coli  communis,  is  a  constant 
inhabitant  of  the  intestine  in  man  and  animals.  In 
nature  it  is  commonly  found  in  soil,  air,  water,  and 
milk.  Just  what  function  it  performs  in  the  intestine 
is  not  known  positively,  but  it  probably  assists  in 
breaking  down  food  materials  into  simpler  form  so 
that  they  can  be  absorbed. 

Once  the  colon  bacillus  has  invaded  the  walls  of 
the  intestine,  it  is  capable  of  setting  up  an  infection. 
It  has  been  found  to  be  the  cause  of  abscess  of  the 
liver,  inflammations  of  the  gall-bladder,  the  urinary 
bladder,  the  pelvis  of  the  kidney,  and  the  pancreas.  It 
is  frequently  the  cause  of  peritonitis  in  cases  of  rup- 

(55) 


56  BACTERIOLOGY. 

tured  appendix.  Occasionally  it  causes  a  general  in- 
fection. The  poisons  of  the  colon  bacillus  are  con- 
tained within  the  body  of  the  organism  and  are 
liberated  only  when  it  disintegrates.  The  knowledge 
of  this  fact  has  made  it  possible  to  immunize  against 
colon  infections  by  injecting  the  dead  cultures,  or 
vaccine,  in  slowly  increasing  doses.  (See  Immunity.) 
On  account  of  its  constant  presence  in  the  intes- 
tine of  man  and  animals,  the  presence  of  the  colon 
bacillus  in  water  or  milk  leads  to  the  assumption  that 
they  have  become  infected  with  intestinal  discharges, 
and  so  not'  safe  for  consumption.  On  account  of  the 
wide  distribution  of  the  colon  bacillus  in  nature,  this 
view  has  been  modified  to  some  extent,  and  now, 
unless  they  are  present  in  excessive  number,  the  water 
or  milk  is  not  condemned. 

THE  BACILLUS  TYPHOSUS. 

The  typhoid  bacillus  is  the  cause  of  typhoid  fever. 
In  recent  years  we  have  come  to*  recognize  that  there 
are  a  number  of  other  micro-organisms  closely  related 
to  the  typhoid  bacillus  which  produce  a  fever  and  other 
symptoms  that  make  a  clinical  picture  identical  with 
typhoid  fever.  It  is  more  accurate  therefore  to  look 
upon  the  clinical  condition  of  typhoid  as  being  clue  to 
any  one  of  a  group  of  micro-organisms  the  chief 
members  of  which  are  the  typhoid,  paratyphoid,  and 
paracolon  bacilli,  with  forms  intermediate  between 
each. 


BACILLI  OF  THE  COLON.  57 

The  typhoid  bacillus  is  both  a  saprophyte  and  a 
parasite.  As  a  saprophyte  it  is  widely  distributed  in 
nature,  due  to  its  ability  to  adapt  itself  to  its  environ- 
ment. It  will  live  in  water,  ice,  sewage,  milk,  dust, 
air,  and  soil.  In  surface-water  typhoid  bacilli  will 
live  about  a  week,  being  rapidly  overgrown  by  other 
bacteria,  but  in  distilled  water  they  will  live  for  three 
months.  Freezing  will  kill  most  of  them  in  a  few 
days.  Experiments  made  by  placing  typhoid  bacilli 


Fig.  6. — Typhoid  bacilli  showing  flagella.     X   1100 
times.     (After  Loffler.) 

in  ice  prove  that  nearly  all  are  killed  in  a  week,  but 
occasionally  they  live  for  three  months.  The  bacillus 
will  retain  life  for  six  months  in  the  upper  layers  of 
the  soil. 

Within  the  body  they  can  resist  the  action  of  the 
gastric  juice  and  multiply  in  the  small  intestine,  where 
the  greatest  amount  of  damage  is  done.  During  the 
disease  the  typhoid  bacilli  may  be  found  in  the  cir- 
culating blood,  spleen,  mesenteric  lymphatic  glands, 
rose-spots,  and  occasionally  in  the  sputum  and 
vomitus.  Typhoid  fever  therefore  should  be  con- 
sidered not  as  a  local  infection  of  the  intestine,  but  as 
a  general  infection  with  the  organisms  present  in  many 


58  BACTERIOLOGY. 

of  the  organs  and  tissues  of  the  body.  In  the  bile, 
urine,  and  stools  the  bacilli  may  persist  for  months 
and  years  after  the  acute  infection  has  passed.  It  is 
for  this  reason  that  complications  and  sequelae  so 
frequently  occur.  The  persistence  of  the  typhoid 
bacilli  in  the  bile  is  an  important  factor  in  the  produc- 
tion of  gall-stones;  the  bacilli  have  been  found  in  the 
centers  of  stones  from  ten  to  fifteen  years  after  the 
infection. 

The  typhoid  bacillus  is  a  short,  rod-shaped 
organism  with  twelve  or  more  flagella,  and  actively 
motile.  It  grows  on  all  the  ordinary  culture  media  in 
the  presence  or  absence  of  oxygen. 

infectkm  Infection  with  typhoid  bacilli  always  occurs  by 

place  wav  °f  tne  alimentary  tract,  by  infected  water  or  food. 
Added  to  the  cause  of  infection  there  is  usually  a 
lowered  resistance  on  the  part  of  the  individual. 

The  infection  reaches  the  alimentary  tract,  most 
often  through  infected  water.  As  we  have  seen, 
typhoid  bacilli  will  live  for  months  in  the  soil ;  so  that 
the  discharges  from  typhoid  patients  that  have  not 
been  disinfected  and  are  deposited  in  or  on  the  ground 
may  lead  to  the  infection  of  nearby  wells  and  streams, 
particularly  during  periods  of  heavy  rain.  Water 
infected  in  this  way  may  give  rise  to*  local  epidemics 
in  the  case  of  wells,  or  to  epidemics  miles  away  in 
the  case  of  streams.  The  epidemic  of  typhoid  fever 
in  Ithaca,  N.  Y.,  in  1903  was  caused  by  the  infection 
of  the  city  water-supply  by  a  case  of  typhoid  in  a 
laborers'  camp  situated  on  the  banks  of  the  stream  that 


BACILLI  OF  THE  COLON.  59 

fed  the  city  reservoir;  1500  cases  of  typhoid  occurred 
in  a  remarkably  short  time. 

Wells  are  sometimes  infected  from  privies,  cis- 
terns, and  open  cesspools  when  they  are  placed  near  a 
well,  or  when  the  natural  drainage  of  the  soil-water  is 
in  the  direction  of  the  well.  Defective  walls  or  cover- 
ing that  admit  surface-water  render  the  infection  of 
wells  in  this  way  more  likely. 

Milk  is  an  excellent  culture  medium,  and  typhoid 
bacilli  will  grow  readily  in  it.  They  gain  entrance  to 
the  milk  by  washing  the  milk  cans  or  pails  in  infected 
water,  or  from  the  hands  of  persons  sick  or  but 
recently  recovered  from  the  disease.  Flies  may  also 
carry  the  infection  to  milk.  There  have  been  some 
185  epidemics  of  typhoid  traced  to  milk.  In  1903  a 
milkman  in  Boston  sick  with  typhoid  spread  the  dis- 
ease through  the  milk,  causing  an  epidemic  of  over 
400  cases. 

The  infection  may  be  spread  by  eating  uncooked 
vegetables  that  have  been  washed  in  infected  water. 
Oysters  and  clams,  when  they  have  been  grown  in 
water  contaminated  with  sewage,  have  been  known  to 
carry  the  infection.  Along  the  seaboard  laws  are  now 
in  force  that  prohibit  the  cultivation  of  oysters  in 
water  near  the  outlet  of.  sewers.  The  importance  of 
flies  in  the  spread  of  typhoid  has  been  recognized  only 
in  the  last  ten  years.  When  they  come  in  contact  with 
typhoid  patients,  or  with  infected  discharges,  they 
carry  the  bacilli  on  their  bodies  and  deposit  them  on 
foodstuffs. 


60  BACTERIOLOGY. 

Typhoid  Finally,  typhoid  is  spread  by  what  are  known  as 

carriers 

carriers,  or  persons  that  carry  the  bacilli  in  their  bodies 
for  a  long  time  after  they  have  recovered  from  the 
disease.  About  4  per  cent,  of  all  typhoid  cases  be- 
come carriers.  The  bacilli  may  be  voided  in  the  urine 
or  passed  in  the  stools.  Dr.  Park  tells  of  a  cook  who 
carried  typhoid  bacilli  in  the  stools.  During  a  period 
of  five  years  she  had  been  employed  in  six  different 
families  in  which  26  cases  of  typhoid  fever  had  de- 
veloped, all  within  a  month  after  her  arrival  in  each 
family 

preven-  To  limit  the  spread  of  typhoid  fever,  precautions 

should  be  taken  to  render  all  food  materials  and  water 
free  from  infection  and  to  destroy  the  typhoid  bacilli 
in  all  discharges  that  may  contain  them.  During 
times  of  epidemics  special  care  should  be  taken  to  boil 
all  drinking-water,  to  pasteurize  all  milk  drunk,  and 
to  wash  all  vegetables  to  be  eaten  uncooked  in  boiled 
water. 

So  far  as  the  destruction  of  the  bacilli  in  the  dis- 
charges is  concerned,  the  disinfection  of  the  urine  and 
stools  is  of  the  utmost  importance.  The  stools  are 
best  disinfected  with  a  5  per  cent,  solution  of  carbolic 
acid.  The  solid  parts  should  be  broken  up  with  a 
stick  that  can  be  burned  or  with  a  glass  rod  that  can  be 
sterilized  after  using,  in  order  that  all  parts  of  the 
stool  may  come  into  contact  with  the  disinfecting  fluid. 
Stools  treated  in  this  way  should  be  allowed  to  stand 
for  at  least  one  hour;  then  thrown  into  the  closet, 
buried,  or  burned.  In  the  country  they  should  be 


BACILLI  OF  THE  COLON.  61 

thrown  into  a  trench  so  placed  that  the  surface  drain- 
age is  away  from  the  well  or  the  nearest  water-course. 
Quicklime  should  cover  the  stool  in  the  trench-  and 
over  this  dirt  should  be  thrown.  The  urine  should  be 
disinfected  with  carbolic  acid  solution  in  the  same 
manner.  All  urinals  and  bed-pans  must  be  disinfected 
with  carbolic  solution  after  being  used. 

The  patient  should  have  eating  utensils  and  toilet 
articles  for  his  own  exclusive  use,  which  should  be 
marked  and  kept  separate  from  all  others.  Remnants 
of  food  should  be  burned  or  disinfected  away  from 
the  kitchen. 

Nurses  and  attendants  "on  typhoid  patients  must 
always  wash  their  hands  after  handling  the  patient  in 
a  i :  1000  solution  of  bichloride  of  mercury.  Uni- 
forms and  linen  that  have  been  worn  in  the  patient's 
room  should  be  soaked  in  carbolic  solution  before  be- 
ing taken  to  the  laundry.  Nurses  should  not  eat  in 
the  same  room  with  typhoid  patients.  The  direct 
infection  from  patient  to  nurse  is  not  at  all  uncommon, 
and  the  directions  just  given  must  be  strictly  observed. 

After  recovery  the  patient  should  be  given  a  full 
bath  before  leaving  the  room,  and  the  room,  itself 
disinfected  in  the  usual  way. 

Infection  with  the  typhoid  bacillus  is  followed  by 
an  immunity  to  the  disease  which  persists  for  a  vari- 
able length  of  time,  sometimes  for  life.  Instances  of 
reinfection  are  rare.  The  immunity  is  conferred  by 
the  presence  in  the  blood  of  protective  substances 
known  as  bacteriolysins  and  agglutinins.  The  former 


62  BACTERIOLOGY. 

are  very  much  increased  after  typhoid,  and  by  experi- 
ment it  can  be  shown  that  the  blood  of  patients  after 
recovering  from  typhoid  has  marked  power  to  dis- 
solve the  typhoid  organisms.  The  agglutinins  possess 
the  power  of  drawing  the  typhoid  bacilli  into  clusters 
or  clumps.  This  phenomenon  is  made  use  of  in  de- 
tecting the  presence  of  typhoid  fever  by  what  is  known 
widai  as  the  Widal  reaction.  It  is  made  in  this  way:  A 

reaction 

small  amount  of  blood  is  drawn  into  a  capillary  tube 
from  the  patient's  ear  and  allowed  to  clot.  By  clotting 
the  serum  is  separated  from  the  blood.  The  object 
of  the  test  is  to  see  if  the  serum  contains  any  agglu- 
tinins of  typhoid  bacilli.  All  blood  contains  a  small 
amount  of  agglutinating  substance;  so  the  serum  is 
diluted,  say,  to  i  :  50  or  i  :  100  and  mixed  with  a  fresh 
bouillon;  culture  of  typhoid  bacilli  in  equal  parts.  The 
mixture  is  now  watched  under  the  microscope,  and  if 
the  agglutinins  are  present  the  typhoid  bacilli  will  be 
seen  drawn  together  into  clumps  or  clusters  and  lose 
their  motility.  When  clumping  is  complete  the  re- 
action is  said  to  be  positive,  and  means  that  the  pa- 
tient now  has  or  recently  has  had  typhoid  fever. 
Negative  reactions  are  of  no  significance,  as  the 
reaction  is  not  constant,  being  present  one  day  and 
absent  the  next.  A  positive  reaction,  however,  is 
conclusive. 

Quite  recently  the  prevention  of  typhoid  has  been 


immunity   greatly  advanced  by  what  is  known  as  vaccination.    As 

V  - 

mentioned  earlier  in  the  chapter,   the  poison  of  the 
typhoid  bacilli  is  found  within  the  body  of  the  cells, 


BACILLI  OF  THE  COLON. 


63 


and  is  liberated  only  after  death  and  disintegration  of 
the  organisms.  An  active  immunity  to  the  disease 
can  be  produced  by  injecting  the  killed  typhoid  bacilli, 
which  after  disintegration  set  free  their  poisons  in  the 
blood  and  stimulate  the  organs  and  tissues  of  the  body 
to  form  protective  substances  that  prevent  infection. 
This  method  of  creating  immunity  to  typhoid  has  been 


c.  D. 

Fig.  7.— Stages  of  the  Widal  reaction.     (After  Robin.) 

practised  a  great  deal  in  the  last  two  years  with  very 
gratifying  results.  It  was  first  tried  in  this  country  in 
the  U.  S.  Army  maneuver  camp  at  San  Antonio, 
Texas;  8097  men  were  vaccinated,  that  is,  they  were 
injected  with  a  killed  culture  of  typhoid  bacilli  on 
three  occasions,  the  dose  being  increased  each  time. 
Only  one  case  developed  among  these  men,  and  this 
one  was  not  fatal. 

Among  nurses  and  hospital  attendants  the  anti- 


64  BACTERIOLOGY. 

typhoid  vaccination  is  being  largely  practised.  In  the 
Massachusetts  General  Hospital  1381  nurses  and 
attendants  were  vaccinated  with  no  cases  of  typhoid 
developing  subsequently. 

The  injections  are  usually  made  in  the  arm,  and 
are  followed  rarely  by  a  reaction  marked  by  fever, 
headache,  and  malaise.  This  occurs  in  only  i  per 
cent,  of  the  cases. 

THE  BACILLUS  PARATYPHOSUS. 

The  paratyphoid  bacillus  in  shape  and  size  is  very 
much  like  the  typhoid  bacillus.  It  is  differentiated 
from  the  typhoid  bacillus  by  its  ability  to  ferment 
glucose.  There  are  two  types  of  paratyphoid  bacilli, 
called  type  A  and  B,  which  differ  slightly  in  their 
method  of  growth.  They  also  behave  differently  in 
the  agglutination  or  Widal  reaction.  The  blood  of 
patients  sick  with  paratyphoid  fever  will  not  agglu- 
tinate the  typhoid  bacillus.  If  the  infection  is  due  to 
paratyphoid  A  the  blood  will  not  agglutinate  the 
paratyphoid  B,  but  only  the  A. 

The  agglutination  reactio-n  is  a  very  good  way  to 
diagnose  the  type  of  infection  present  in  all  cases  of 
typhoid-like  infection. 

The  course  of  the  fever  in  paratyphoid  infections 
is  somewhat  milder  and  shorter  than  in  typhoid.  In 
the  fatal  cases  coming  to  autopsy  the  spleen  and 
mesenteric  glands  are  enlarged  just  as  in  typhoid,  but 
the  intestines  show  little  change.  Changes  in  the 


BACILLI  OF  THE  COLON.  65 

bowel  do  occur  because;  hemorrhage  sometimes  occurs 
in  paratyphoid  fever. 

Immunity  follows  an  attack  of  paratyphoid  fever 
just  as  in  true  typhoid,  but  the  protection  is  only 
against  the  type  of  paratyphoid  bacillus  causing  the 
infection.  A  case  illustrating  this  point  came  under 
the  writer's  observation  in  the  summer  of  1913,  in 
which  the  patient  developed  typhoid-like  symptoms 
and  fever,  although  he  had  had  a  severe  typhoid  in- 
fection only  a  few  years  before.  The  infection  proved 
to  be  a  paratyphoid  type  B. 

In  the  immunization  against  typhoid  with  killed 
cultures  it  is  now  customary  to  use  the  killed  bacilli 
of  both  typhoid  and  paratyphoid  in  order  to>  confer 
immunity  to  all  types  of  typhoid-like  organisms. 

THE  BACILLI  OF  THE  DYSENTERY  GROUP. 

The  first  member  of  this  group  was  discovered  by 
Shiga,  a  Japanese,  in  1897.  In  its  size  and  shape  it 
is  very  much  like  the  colon  bacillus,  but  does  not  fer- 
ment sugars  like  the  colon  bacillus  does.  It  can  be 
grown  from  the  surface  of  the  large  bowel  or  from 
the  stools  of  dysenteric  patients,  and  cultures  when 
fed  to  dogs  cause  dysentery. 

In  man  the  dysentery  bacilli  will  give  rise  to 
severe  diarrhea,  accompanied  with  cramps,  tenesmus, 
and  fever.  The  stools  are  streaked  with  blood  and 
contain  mucus.  The  disease  spreads  rapidly,  some- 
times through  infected  water,  sometimes  from  direct 


66  BACTERIOLOGY. 

contact.  It  lasts  from  seven  to  ten  days,  and  fre- 
quently is  attended  with  a  death  rate  of  from  5  to  20 
in  100. 

Numerous  epidemics  have  been  reported  in  the 
United  States;  among  them,  an  epidemic  of  350  cases 
in  the  village  of  Tuckahoe,  N.  Y.,  which  was  studied 
by  the  writer,  together  with  Dr.  Wm.  H.  Park.  The 
cause  of  the  epidemic  was  found  to  be  due  to  an  or- 
ganism almost  identical  with  the  one  described  by 
Shiga.  From  a  study  of  the  dysentery  bacilli  found 
in  this  and  other  epidemics  in  this  country,  we  find 
that  there  are  a  number  of  bacilli  very  nearly  alike 
that  may  cause  these  epidemics  of  dysentery. 

Individuals  that  have  been  infected  with  dysen- 
tery bacilli  develop  agglutinating  substances  in  the 
blood  that  will  clump  the  dysentery  bacilli  just  as  in 
the  case  of  typhoid  and  paratyphoid  infections. 

To  summarize  what  has  been  said  of  the  colon- 
typhoid-dysentery  group:  All  the  members  are  bacilli 
of  similar  appearance,  all  are  to  some  degree  motile, 
but  they  differ  one  from  another  in  their  manner  of 
growth,  particularly  in  their  ability  to  ferment  sugars. 
The  colon  group,  although  a  constant  inhabitant  of 
the  intestine,  gives  rise  to  no  infection  unless  it  gains 
access  to  tissues  outside  the  bowel.  The  typhoid  and 
dysentery  bacilli  are  never  present  in  the  body  under 
normal  conditions,  but  when  they  enter  the  body  they 
cause  a  characteristic  infection.  The  blood-serum  of 
all  infected  individuals  develops  substances  that  pro- 
tect against  reinfection,  and  among  these  substances 


BACILLI  OF  THE  COLON.  67 

are  the  agglutinins  which  gather  the  bacilli  together 
into  clumps.  The  agglutinins  caused  by  infection  with 
the  colon  bacillus  will  agglutinate  only  the  colon 
bacillus ;  the  same  is  true  for  the  typhoid,  paratyphoid, 
and  dysentery  bacilli.  This  peculiarity  is  made  use  of 
in  diagnosing  the  kind  of  infection  present. 

THE  Mucosus  CAPSULATUS  GROUP. 

In  this  group  are  placed  a  number  of  micro- 
organisms which  resemble  one  another  closely  in  their 
morphology  and  manner  of  growth.  The  members  of 
this  group  differ  but  little  from  those  of  the  colon 
group. 

THE  BACILLUS  Mucosus  CAPSULATUS. 

This  bacillus  was  discovered  by  Friedlander  in 
1883,  and  is  often  called  the  Friedlander  bacillus.  It 
is  a  short,  plump  bacillus,  with  rounded  ends,  exhibit- 
ing considerable  variation  in  size.  It  may  occur 
singly,  in  pairs,  or  in  chains.  It  is  not  motile  and 
forms  no  spores.  On  all  the  ordinary  culture  media  it 
grows  readily  even  at  room  temperature.  The  most 
characteristic  feature  is  the  transparent  capsule  about 
the  organism.  Exposure  to  heat  of  60°  C.  destroys 
the  bacillus  in  a  short  time. 

At  the  time  of  its  discovery  this  bacillus  was  be- 
lieved to  be  the  chief  cause  of  lobar  pneumonia,  but 
it  has  since  been  proved  that  it  is  responsible  for  only 
a  small  percentage  of  the  cases.  In  addition  to  caus- 


68  BACTERIOLOGY. 

ing  pneumonia,  it  has  been  found  in  suppurations  of 
the  nasal  sinuses,  empyema,  pericarditis,  and  menin- 
gitis. No  method  of  immunization  has  been  found  as 
yet. 

THE  BACILLUS  LACTIS  AEROGENES. 

The  Bacillus  lactis  aerogenes  is  constantly  present 
in  milk  and,  with  other  micro-organisms,  is  the  cause 
oi  souring.  It  is  also  present  in  water,,  sewage,  and 
feces.  It  closely  resembles  the  colon  bacillus,  but 
differs  from  it  chiefly  in  being  non-motile  and  ha,ving 
•a  capsule.  It  is  not  a  virulent  organism,  but  has  been 
known  to  be  the  cause  of  cystitis. 


THE  BACILLI  OF  THE  PROTEUS  GROUP. 

The  members  of  this  group  are  putrefactive  bac- 
teria capable  of  breaking  down  complex  proteids  into 
simpler  compounds.  They  are  widely  distributed, 
being  found  in  water,  soil,  air,  and  wherever  putre- 
faction is  in  progress. 

The  chief  member  of  the  group  is  the  Bacillus 
proteus  vulgaris,  a  large,  thick  bacillus  that  grows 
readily  on  the  ordinary  media.  It  is  motile,  but  forms 
no  spores.  It  liquefies  gelatin  in  its  growth  and  pro- 
duces a  characteristic  odor  of  putrefaction.  It  is  not 
a  very  virulent  organism.  It  occasionally  causes  peri- 
tonitis, endometritis,  pyelonephritis,  and  enteritis.  It 
has  been  described  as  the  cause  of  several  epidemics  of 
meat  poisoning. 


BACILLI  OF  THE  COLON.  69 

THE  BACILLUS  OF  RHINOSCLEROMA. 

This  bacillus  is  a  short,  plump  rod,  in  appearance 
and  manner  of  growth  almost  identical  with  the 
Bacillus  mucosus  capsulatus.  Infection  with  this 
micro-organism  is  located  usually  in  the  mucous  memr 
brane  of  the  nose,  mouth,  pharynx,  and  larynx.  It 
produces  hard,  nodular,  inflammatory  swellings. 
Under  the  microscope  large,  swollen  cells  are  found  in 
the  tissue  which  contain  the  bacilli. 


CHAPTER  VII. 
BACTERIA  CAUSING  ACUTE  INFECTIONS. 

THE  BACILLUS  OF  TETANUS. 

TETANUS,  or  lockjaw,  as  it  is  more  commonly 
called,  has  existed  for  many  centuries,  but  the  micro- 
organism causing  the  infection  was  not  discovered 
until  1885,  when  Nicolaier,  a  German  bacteriologist, 
was  successful  in  producing  the  disease  in  animals  by 
injecting  them  with  small  amounts  of  soil, 
rphoi-  The  organism  is  a  bacillus  of  large  size,  which 

forms  spores  readily.  It  grows  on  the  ordinary  cul- 
ture media,  but  only  when  no  oxygen  is  present.  The 
spores  are  located  at  one  end  of  the  bacillus,  and  cause 
a  swelling  which  gives  it  much  the  same  shape  as  a 
drumstick.  The  spores  are  very  resistant  to  harmful 
influences.  They  will  survive  dry  heat  of  80°  C.  for 
an  hour  and  5  per  cent,  carbolic  acid  solution  for 
twelve  to  fifteen  hours.  Away  from  sunlight  the 
spores  may  live  for  years. 

Its  natural  home  is  the  soil,  especially  where  it 
has  been  cultivated  and  manured.  This  is  due  to  the 
fact  that  tetanus  bacilli  are  present  in  the  intestines  of 
some  animals.  In  the  United  States  the  soil  in  the 
Hudson  Valley  and  on  Long  Island  seems  particularly 
infectious. 

Infection  generally  occurs  by  the  contamination 
(70) 


CAUSING  ACUTE  INFECTIONS. 


71 


of  lacerated  wounds,  especially  gunshot  wounds  with 
particles  of  wood,  soil,  or  glass.  A  great  many  cases 
in  our  country  have  been  due  to  wounds  caused  by  fire- 
crackers and  blank-cartridge  pistols,  and  has  led  to  a 
crusade  against  their  use  on  Independence  Day.  The 


Path    of 
infection 


Fig.  8. — Tetanus  bacilli.  Spore-bearing  rods  from  an  agar 
culture.  Mounted  preparations,  stained  with  fuchsin.  X  1000. 
(Frankel-Pfeiffer.) 

period  of  incubation  is  from  one  to  twenty  days.  The 
muscular  spasm  generally  begins  in  the  muscles  of  the 
face  and  jaw,  making  it  difficult  to  chew.  This  is  the 
origin  of  the  popular  name,  lockjaw.  Gradually 
other  muscles  become  tight  and  stiff  until  finally  all 
the  muscles  of  the  trunk  and  extremities  are  affected. 
The  least  irritation  is  sufficient  to  throw  all  the  muscles 


72  BACTERIOLOGY. 

into  spasm,  making  the  entire  body  rigid.  These 
spasms  are  produced  by  soluble  poisons  that  are 
formed  by  the  tetanus  bacilli  at  the  point  of  inocula- 
tion,  and  seem,  to  have  a  special  affinity  for  the  tissues 
of  the  brain  and  spinal  cord.  The  poisons  are  also 
formed  in  the  culture  media,  and  are  among  the  most 
powerful  known ;  the  poison  formed  in  a  bouillon  cul- 
ture being  sufficient  to  cause  death  when  injected  into 
mice  in  doses  of  0.0000005  c.c.  Man  and  the  horse  are 
very  susceptible  to  the  poison,  while  chickens  are  able 
to  resist  large  doses. 

immunity  It   is  possible  to   immunize   animals   against  the 

tetanus  toxin  by  injecting  the  poison  in  very  small 
doses  and  gradually  increasing  it.  In  time  the 
animal  can  withstand  large  doses  without  ill  effect. 
The  antitoxin  for  tetanus  is  made  by  injecting  the 
poison  in  ascending  doses  into  horses  until  they  are 
thoroughly  immunized;  then  they  are  bled  and  the 
serum,  which  contains  the  protective  substance,  is  used 
to  inject  into  human  beings.  The  use  of  tetanus  anti- 
toxin has  not  been  attended  with  as  much  success  as 
the  antitoxin  of  diphtheria.  When  the  symptoms  of 
lockjaw  develop  it  means  that  the  toxin  has  already 
attacked  the  brain  and  spinal  cord ;  so  the  antitoxin  is 
of  little  use.  To  be  effective  it  must  be  given  at  the 
time  of  the  infection  or  shortly  after. 

THE  GLANDERS  BACILLUS  (BACILLUS  MALLEI). 

Glanders   is   a  malady  which   occurs   principally 
among  horses,  but  dogs,  cats,  sheep,  and  swine  are 


CAUSING  ACUTE  INFECTIONS.  73 

also  susceptible.  In  rare  instances  man  acquires  the 
disease.  It  is  caused  by  the  Bacillus  mallei,  a  small, 
rod-shaped  organism  with  rounded  ends.  It  can  be 
cultivated  easily  on  the  ordinary  kinds  of  culture 
media,  and  stains  readily,  but  unevenly,  giving  the 
bacillus  a  granular  appearance  much  like  the  bacillus  of 
diphtheria.  Heat  at  60°  C.  will  destroy  the  bacilli  in 
two  hours  and  i  per  cent,  carbolic  acid  in  thirty 
minutes.  Drying  destroys  them  in  a  short  time.  In 
water  they  may  live  for  two  months  or  more. 

The  infection  in  horses  occurs  generally  in  the 
nose  or  mouth,  from  the  entrance  of  the  bacilli  through 
cracks  or  wounds  in  the  mucous  membrane.  After  an 
incubation  period  of  two*  or  three  days  there  is  a  nasal 
discharge  with  swelling  of  the  nasal  mucous  mem- 
brane, which  later  ulcerates.  The  cervical  lymphatic 
glands  also  swell  and,  may  suppurate.  The  dis- 
ease frequently  terminates  in  pneumonia.  Infection 
through  the  skin  gives  rise  to  a  nodular  eruption,  the 
nodules  later  undergoing  suppuration.  This  is  called 
farcy. 

The  disease  may  be  transmitted  to  human  beings 
from  infected  horses  or  may  pass  from  man  to  man. 
The  manifestations  of  the  disease  in  man  are  much  the 
same  as  in  the  horse.  It  may  assume  an  acute  or 
chronic  course,  the  former  nearly  always  resulting 
fatally. 

The  toxins  of  the  Bacillus  mallei  are  within  the 
bodies  of  the  organisms,  that  is,  they  are  endotoxins 
and  are  very  resistant  to  heat.  Attempts  have  been 


74      '  BACTERIOLOGY. 

made  to  immunize  animals  by  the  injection  of  small 
amounts  of  the  toxin,  and  have  been  to  some  extent 
successful.  It  is  not  possible  to  immunize  man  in  this 
way. 

Diagnosis  The  diagnosis  of  glanders  may  be  made  in  sev- 

eral ways.  The  discharges  or  the  pus  may  be  injected 
into  the  peritoneal  cavity  of  guinea-pigs.  If  the 
bacillus  of  glanders  is  present  the  testicles  become 
x  swollen  and  painful  in  two  to  five  days.  A  test  may 
be  made  for  the  presence  of  substances  in  the  blood- 
serum  that  will  agglutinate  the  bacilli  of  glanders.  It 
is  done  in  the  same  manner  as  the  Widal  reaction  for 
typhoid  fever.  Finally,  the  toxin  of  the  bacilli  made 
from  cultures  and  called  mallein  may  be  injected  under 
the  skin  of  suspected  cases.  If  glanders  is  present  it 
produces  a  reaction  marked  by  fever  and  tenderness 
about  the  point  of  inoculation.  The  principle  upon 
which  this  reaction  rests  is  the  same  as  in  the  tuber- 
culin reaction. 

THE  BACILLUS  OF  INFLUENZA. 

Influenza,  or  grippe,  is  a  highly  infectious  disease 
that  spreads  with  great  rapidity.  It  is  caused  by  the 
influenza  bacillus.  In'  1889  an  epidemic  of  grippe 
started  in  Russia  and  in  a  year's  time  extended  com- 
pletely around  the  world.  This  bacillus  is  smaller  than 
the  bacilli  we  have  studied  so  far.  It  is  not  motile 
and  does  not  form  spores.  It  grows  only  in  the  pres- 
ence of  oxygen.  It  is  difficult  to  cultivate  unless  fresh 


CAUSING  ACUTE  INFECTIONS.  75 

blood  is  present  on  the  media.  Heat  kills  the  bacillus 
readily;  an  exposure  for  a  few  minutes  at  60°  C.  is 
sufficient.  Drying  also  kills  it  quickly. 

The  infection  manifests  itself  chiefly  in  the  nose, 
throat,  and  bronchi,  but  may  extend  to  the  lungs  and 
give  rise  to  pneumonia.  From  the  nose  the  infection 
often  extends  to  involve  the  accessory  sinuses  and  the 
middle  ear.  Exceptionally  the  infection  may  extend 
to  the  meninges.  During  the  winter  of  1912  the 
writer  found  the  influenza  bacilli  in  the  circulating 
blood  of  a  case  of  septic  endocarditis.  The  incubation 
period  is  from  twenty-four  to  seventy-two  hours  and 
the  onset  is  sudden.  The  bacilli  are  present  in  the  nose 
and  throat;  so  to  prevent  the  spread  to  others  these 
secretions  must  be  collected  and  destroyed.  The 
bacilli  remain  in  the  secretions  of  the  nose,  throat,  and 
bronchi  for  long  periods  after  the  acute  infection  has 
subsided;  in  fact,  it  is  probably  present  all  the  time 
in  the  secretions  of  some -people.  Sporadic  cases  may 
be  explained  by  this  assumption. 

The  immunity  following  influenza  is  of  very  short 
duration,  and  reinfection  is  -very  common.  Artificial 
immunity  has  been  attempted  by  injecting  the  killed 
bacilli,  but  has  not  proved  to  be  very  successful. 

THE  BACILLUS  OF  WHOOPING-COUGH. 

The  bacillus  causing  whooping-cough  was  de- 
scribed first  by  two  French  bacteriologists,  Bordet  and 
Gengou,  in  1900.  It  is  small  in  size,  much  like  the 


76  BACTERIOLOGY. 

bacillus  of  influenza,  but  ovoid  in  shape.  It  is  found 
constantly  in  the  sputum  of  early  cases  of  whooping- 
cough.  It  can  be  cultivated  on  the  usual  culture  media 
if  blood  or  its  coloring  matter  is  present. 

The  infection  localizes  itself  in  the  throat,  nose, 
and  bronchial  tubes,  and  is  spread  by  the  secretions 
from  these  parts.  It  is  transmitted  from  one  child 
to  another,  chiefly  by  direct  contact,  less  often  through 
dwellings  and  schools  that  have  been  infected. 

One  attack  generally  protects  during  life;  so 
cases  of  reinfection  are  very  rare.  The  toxins  of  the 
bacillus  are  within  the  bodies  of  the  bacterial  cells 
(endotoxins).  Efforts  have  been  made  to  immunize 
against  the  disease  and  to  modify  its  course  by  inject- 
ing the  killed  bacteria.  The  results  have  been  fairly 
successful. 

THE  KOCH-WEEKS  BACILLUS. 

This  organism  is  the  cause  of  acute  infectious 
conjunctivitis,  commonly  called  "pink  eye."  It  re- 
sembles closely  the  bacillus  of  influenza,  but  differs 
from  it  in  growing  on. media  that  does  not  contain 
hemoglobin. 

THE  DUCREY  BACILLUS. 

This  bacillus  is  of  very  small  size,  and  has  a 
tendency  to  form  chains.  It  is  not  motile  and  does 
not  form  spores. .  It  stains  with  all  the  ordinary  dyes, 
but  more  deeply  at  the  ends.  It  will  grow  only  on 
media  containing  human  blood. 


CAUSING  ACUTE  INFECTIONS.  77 

Infection  with  this  organism  is  the  cause  of 
chancroid,  or  soft  chancre,  an  acute,  inflammatory, 
ulcerating  sore  which  occurs  generally  on  the  genitals 
and  surrounding  skin.  It  begins  as  a  small  pustule 
which  ruptures  and  becomes  an  ulcer,  having  a  tend- 
ency to  spread.  The  bacilli  frequently  extend  along 
the  lymphatic  vessels  and  involve  the  adjacent  glands 
of  the  groin,  which  may  undergo  suppuration.  The 
bacilli  can  be  found  in  the  pus  and  discharges  from 
the  ulcers.  Infection  results  generally  from  sexual 
contact,  rarely  from  infected  dressings,  towels,  and 
instruments. 

THE  MICROCOCCUS  MELITENSIS  (MALTA  FEVER). 

Malta  fever  occurs  among  the  people  living  on 
the  shores  of  the  Mediterranean  Sea,  in  some  parts  of 
South  America,  and  in  the  West  Indies.  It  is  similar 
to  typhoid  fever,  but  is  not  so  severe,  and  the  mortality 
rate  is  not  so  high.  The  Micrococcus  melitensis,  the 
cause  of  the  infection,  is  readily  cultivated  on  the  ordi- 
nary laboratory  culture  media  and  stains  easily.  It 
appears  under  the  microscope  in  groups  and  short 
chains.  The  infection  is  spread  in  the  milk  of  goats, 
which  is  the  chief  source  of  the  milk-supply  in  Malta, 
and  probably  by  the  mosquito. 

Patients  sick  with  Malta  fever  develop  in  their 
blood  agglutinins  for  the  micrococcus,  which  may  be 
utilized  in  detecting  the  disease.  The  use  of  vaccines 
made  from  killed  cultures  of  the  micrococcus  has  been 
attended  with  good  results. 


78  BACTERIOLOGY. 

THE  BACILLUS  OF  ANTHRAX. 

Anthrax  is  primarily  a  disease  of  cattle  and 
sheep,  although  horses,  hogs,  and  goats  are  suscep- 
tible. The  infection  may  be  transmitted  directly  to 
man  from  infected  animals  or  from  their  hides  or 
wool.  The  disease  exists  for  the  most  part  in  Europe 
and  the  East,  but  in  the  United  States  it  is  rarely  met 
with. 

The  anthrax  bacillus  was  the  first  micro-organism 
definitely  proved  to  be  the  cause  of  a  specific  disease. 
It  is  a  large,  straight  rod  with  square-cut  ends.  It  is 
not  motile.  In  cultures  they  are  prone  to  form  long 
chains  or  threads.  Spores  are  formed,  which  are 
situated  in  .the  center  of  the  bacterial  cells.  They  are 
very  resistant  to  harmful  influences.  While  the  bacil- 
lus itself  may  be  destroyed  by  an  exposure  of  ten 
minutes  to  heat  at  54°  C,  the  spores  require  an  ex- 
posure of  three  hours'  dry  heat  at  140°  C.  and  live 
steam  for  five  to  ten  minutes.  They  will  resist  drying 
for  years.  A  5  per  cent,  solution  of  carbolic  acid  re- 
quires forty  days  to  kill  them,  and  bichloride  of  mer- 
cury i :  1000  forty  minutes.  Direct  sunlight  destroys 
them  in  six  to  twelve  hours. 

Pentary0f  ^hc  ^aci^tls  finds  its  way  into  the  bodies  of  cattle 

principally  through  the  alimentary  tract.  In  man  the 
portal  of  entrance  is  more  often  through  the  skin  and 
respiratory  tract.  Those  handling  live  stock,  butchers, 
and  tanners  are  most  liable  to  contract  the  disease. 
The  first  symptom  of  anthrax  is  a  pustule  or  boil, 


CAUSING  ACUTE  INFECTIONS.  79 

which  progresses  to  ulceration  and  gangrene.  If  this 
is  opened  promptly  recovery  may  follow.  Among 
those  working  on  raw  wool,  hides,  and  horsehair  the 
disease  may  be  acquired  by  inhaling  the  spores.  Infec- 
tion contracted  in  this  manner  causes  a  pneumonia, 
often  called  wool-sorters'  disease. 


Fig.  9. — Anthrax  bacilli.  Spore  formation  and  spore  germi- 
nation. A,  from  the  spleen  of  a  mouse  after  twenty-four  hours' 
cultivation  in  aqueous  humor.  Spores  arranged  in  rods  like  a 
string  of  pearls.  X  650.  B,  germination  of  spores.  X  650.  C, 
the  same,  greatly  magnified.  X  1650.  (Koch.) 

The  disease  is  prevented  from  spreading  by 
destroying  the  infected  animals,  burying  their  bodies 
and  disinfecting  the  stables. 

No  toxins  are  formed  by  the  anthrax  bacillus.     It    immunity 
is    possible    to    immunize    animals    by    injecting    the 
bacilli  that  have  been  attenuated  by  long  growth  at  a 
temperature  of  42°  C.     The  blood-serum  of  animals 
immunized   in   this  way  contains  the  protective   sub- 


80  BACTERIOLOGY. 

stances,   and  may  be  used  to  develop  a  passive  im- 
munity in  other  animals. 

THE  BACILLUS  OF  PLAGUE  (BACILLUS  PESTIS). 

The  bacillus  of  bubonic  plague  was  discovered  by 
Kitasato  and  Yersin  during  the  epidemic  in  China  in 

1893.  It  is  a  short,  thick  bacillus  with  rounded  ends. 
In  old  cultures  atypical  forms  are  found,  some  like 
cocci,  others  club-shaped  like  the  diphtheria  bacillus. 
It  stains  more  deeply  at  the  ends  than  in  the  center. 
It  is  not  motile  and  does  not  form  spores.     It  will 
grow  only  .in  the  presence  of  oxygen.     In  dark,  moist 
places  the  organism  will  live  for  months  or  years.     In 
the  sputum  and  pus  from  patients  it  lives  for  one  or 
two  weeks.     In  cadavers  they  may  live  for  several 
weeks.     Dry  heat  destroys  the  bacillus  in  one  hour, 
boiling  in   a   few  minutes.     Direct  sunlight   requires 
four  or  five  hours.     Carbolic  acid   (5  per  cent.)   and 
bichloride  of  mercury  ( I  :  1000)  destroy  them,  in  ten 
minutes. 

The  plague  raged  from  the  sixth  to  the  seven- 
teenth century,  and  in  the  fourteenth  century  the 
black  death,  as  it  was  called,  destroyed  one-quarter  of 
the  population  of  Europe.  The  great  plague  in  Lon- 
don in  1665  destroyed  70,000  people.  The  disease 
subsided  then  and  remained  practically  dormant  until 

1894,  when  it  broke  out  in  Hong  Kong.     It  spread 
thence  to  other  countries,   and  a  small  epidemic  oc- 
curred in  San  Francisco  in  1907. 

The  infection  may  enter  through  the  skin  or  by 


CAUSING  ACUTE  INFECTIONS.  81 

way  of  the  respiratory  tract,  and  the  symptoms  of  the 
disease  manifest  themselves  after  an  incubation  period 
of  three  to  seven  days.  The  symptoms  following  in- 
fection through  the  skin  are  characterized  by  headache, 
high  fever,  stiffness  in  the  limbs,  restlessness,  and 
anxiety.  Collapse  frequently  follows.  The  lymphatic 
glands  are  enlarged,  particularly  those  in  the  inguinal 
region,  which  are  called  buboes.  Infection  by  way  of 
the  respiratory  tract  begins  abruptly  with  pneumonia. 
The  mortality  rate  for  this  disease  is  very  high, — 80 
to  90  per  cent. 

The  bacilli  of  the  plague  are  present  in  the  swollen  the  disease 

is  spread 

lymphatic  glands,  the  sputum,  urine,  and  intestinal 
discharges,  and  the  infection  may  be  spread  directly 
from  these  sources.  The  chief  way,  however,  in  which 
the  infection  is  spread  is  from  the  bites  of  the  rat-flea, 
which  transmits  the  disease  from  rat  to  rat  and  from 
rat  to  man.  Unsanitary  conditions  have  little  to  do 
with  the  occurrence  of  the  plague,  except  that  they 
favor  infestation  with  rats.  To>  prevent  the  disease 
from  spreading,  all  patients  must  be  quarantined,  all 
discharges  destroyed,  and  all  articles  that  have  come 
in  contact  with  the  patient  disinfected.  To  prevent  ways  of 
rats  from,  breeding,  all  stables  and  outhouses  should  be 
cleaned  up,  and  all  possible  sources  of  food-supply  cut 
off.  Dwelling-houses  should  be  made  rat-proof  as  far 
as  possible.  The  importation  of  the  disease  into  ports 
not  infected  should  be  guarded  against  by  fumigating 
ships  from  infected  countries  and  the  isolation  of  sus- 
pected cases  during  the  period  of  incubation. 


82  BACTERIOLOGY. 

The  toxins  of  the  Bacillus  pestis  are  both  endo- 
and  extra-  cellular.  It  is  possible  to  immunize  animals 
and,  in  their  blood,  substances  that  will  agglutinate 
the  bacilli  are  found.  They  may  be  used  in  the  diag- 
nosis of  the  disease.  In  human  beings  an  immunity 
develops  after  one  attack.  A  protective  serum'  has 
been  used  against  the  disease,  and  is  said  to  reduce  the 
mortality  rate  20  to  25  per  cent. 

THE  BACILLUS  PYOCYANEUS. 

The  discharges  from  open  wounds  occasionally 
have  a  green  color,  the  cause  of  the  color  in  these  cases 
being  due  to  a  pigment  formed  by  the  Bacillus  pyo- 
cyaneus.  It  is  a  short,  actively  motile  rod,  having  a 
tendency  to  form  chains  in  fluid  media.  It  can  be 
readily  cultivated  in  the  presence  of  oxygen,  and  is 
easily  identified  because  it  stains  the  media  upon  which 
it  grows  a  brilliant  green.  It  forms  no  spores. 

This  organism  possesses  no  great  virulence,  and 
may  live  without  producing  injury  on  the  skin,  and  in 
the  respiratory  and  intestinal  tracts  of  animals  and 
man.  It  may,  however,  be  the  cause  of  serious  infec- 
tions, but  in  such  cases  it  is  due  to  greatly  lowered 
resistance  in  the  patient  rather  than  to  the  virulence  of 
the  bacillus.  It  may  be  the  cause  of  otitis  media  and 
diarrhea  and  gastroenteritis  in  children.  Cases  of 
general  sepsis,  liver  abscess,  and  pericarditis  have  been 
attributed  to  it. 

The  pigment  produced  is  of  two  kinds;  one  is 


CAUSING  ACUTE  INFECTIONS.  83 

called  pyocyanin,  soluble  in  chloroform:;  the  other  is 
a  fluorescent  pigment  soluble  in  water.  In  old  cul- 
tures a  ferment-like  substance  is  formed  called  pyo- 
cyanase,  which  has  the  property  of  dissolving  some  of 
the  other  forms  of  bacteria.  It  has  been  used  to 
destroy  diphtheria  bacilli  that  persist  in  the  throat 
after  recovery.  The  toxins  formed  by  the  bacillus  are 
both  endo-  and  extra-  cellular.  Immunity  in  animals 
is  produced  with  much  difficulty,  but  in  man  no-  way 
of  producing  immunity  has  been  devised. 

THE  SPIRILLUM  OF  ASIATIC  CHOLERA. 

The  micro-organism  causing  cholera  is  a  small, 
curved  rod,  often  shaped  like  a  comma,  and  therefore 
called  the  comma  bacillus.  When  two  are  placed  end 
to  end  they  are  S-shaped.  True  corkscrew  forms 
occur,  particularly  in  cultures  in  fluid  media.  The 
spirillum  was  discovered  by  Professor  Koch  in  1884. 
It  is  motile,  being  propelled  by  a  single  flagellum 
placed  at  one  end,  and  grows  on  all  the  laboratory 
media  in  the  presence  of  oxygen.  No  spores  are 
formed. 

Cholera  exists  constantly  in  India  and  countries 

'  tion    of 

of  the  Orient.  It  has  been  carried  occasionally  to  the  digease 
other  countries,  causing  epidemics,  A  very  bad  epi- 
demic occurred  in  Hamburg  in  1892.  In  this  country 
the  disease  has  been  imported  on  several  occasions, 
but  no  epidemic  has  developed  since  1873.  Strict 
measures  are  taken  at  the  chief  ports, — New  York, 


84  BACTERIOLOGY. 

New  Orleans,  and  San  Francisco, — to  quarantine  all 
suspects  among  the  immigrants. 

Infection  always  takes  place  by  way  of  the  ali- 
mentary tract,  from  infected  water  and  food.  While 
infected  water  is  the  most  common  cause,  the  infection 
may  be  carried  on  vegetables  that  have  been  washed 
in  infected  water,  particularly  those  used  as  salads. 
Flies  can  deposit  the  infection  on  bread,  butter,  meat, 
and  other  foodstuffs.  Direct  infection  from  handling 
soiled  bed-linen  is  not  uncommon,  as  is  shown  by  the 
greater  frequency  of  the  disease  among  washerwomen 
during  epidemics.  The  onset  of  cholera,  following  an 
incubation  period  of  two  to  five  days,  is  sudden,  with 
frequent  watery  stools,  high  fever,  and  great  prostra- 
tion. In  the  severe  cases  death  may  occur  in  eight  to 
twelve  hours.  The  infection  localizes  itself  in  the 
intestine.  The  spirilla  are  never  found  in  the  cir- 
culating blood,  consequently  the  stools  alone  are  in- 
fectious and  may  continue  to  be  for  months  after  re- 
covery. People  who  carry  the  spirilla  of  cholera  in 
the  intestine  after  recovery  are  called  cholera  carriers. 
Prevention  To  prevent  the  disease  during  epidemics  all 

drinking-water  and  milk  must  be  boiled,  and  no  meat 
or  vegetables  eaten  unless  cooked.  Great  care  must  be 
taken  to  exclude  flies  from  contact  with  foods.  Bed- 
linen,  clothing,  and  utensils  used  by  patients  should  be 
soaked  in  5  per  cent,  carbolic  solution,  and  subse- 
quently boiled  in  the  laundry.  Attendants  upon 
cholera  patients  should  be  careful  to  disinfect  the  hands 
after  handling  the  patients.  The  stools  are  best  dis- 


CAUSING  ACUTE  INFECTIONS.  85 

infected  with  5  per  cent,  carbolic  solution,  and  the 
disinfection  should  be  continued  for  some  time  after 
recovery. 

The  constitutional  symptoms  that  accompany 
cholera  are  due  to  the  toxins  formed  by  the  spirilla  in 
the  intestines.  They  are  partly  thrown  out  by  the 
organisms,  that  is,  soluble  toxins,  and  partly  retained 
in  the  body  of  the  bacterial  cells  and  set  free  only 
after  their  death.  It  is  possible  to  immunize  animals  Immunity 
against  cholera  by  injecting  small  amounts  of  the 
killed  cultures  or  very  small  doses  of  the  living  organ- 
isms. The  blood-serum1  of  animals  immunized  in  this 
way  contains  substances  that  dissolve  the  spirilla — 
bacteriolysins,  and  substances  that  clump  them; — 
agglutinins.  The  agglutinins  are  made  use  of  in  diag- 
nosing cholera  in  the  same  way  as  in  the  diagnosis  of 
typhoid  fever  (see  Widal  reaction).  Human  beings 
that  have  recovered  from  cholera  are  immune  to  the 
disease,  but  they  remain  so  for  only  a  few  months. 
Efforts  to  protect  human  beings  by  injecting  the  killed 
cultures  have  been  made  in  India  on  a  large  scale,  but 
the  results  have  been  only  partially  successful. 


THE  BACILLUS  OF  DIPHTHERIA. 

Diphtheria  is  an  infectious  disease  caused  by  the 
diphtheria  bacillus,  sometimes  called  the  Klebs-Loffler 
bacillus,  after  the  two  men  who  discovered  it.  The 
word  diphtheria  is  derived  from  a  Greek  word  mean- 
ing leather,  because  of  the  characteristic  false  mem- 


86  BACTERIOLOGY. 

brane  that  forms  in  the  throat.  The  bacillus  causes 
infection  most  frequently  in  the  throat  or  nose,  al- 
though it  may  grow  on  the  gums  or  about  the  teeth. 
It  is  possible  for  diphtheria  bacilli  to  cause  infection 
of  the  middle  ear,  the  sinuses  of  the  nose,  and  the 
lung  (pneumonia).  Rarely  it  extends  to  the  skin 
about  the  mouth,  or  to  the  gen  i  tali  a  or  rectum, 
rphoi-  The  diphtheria  bacillus  is  one  of  the  few  types 

that  can  be  identified  by  its  appearance  under  the 
microscope,  because  its  shape  is  different  from  other 
bacteria.  Three  fairly  distinct  forms  are  recognized : 

A.  The  granular  type,  the  granules  generally  at 
the  ends. 

B.  The  barred  type,  the  granules  so  arranged  that 
the  cell  looks  cross-striped  like  a  barber's  pole. 

C.  The  solid  type,  with  ends  often  club-shaped. 

They  will  grow  on  most  of  the  laboratory  media,  but 
thrive  best  on  media  that  contains  blood-serum. 

It  stains  readily  with  dyes,  is  not  motile,  and 
forms  no  spores.  Outside  the  body  direct  sunlight 
kills  the  bacilli  in  half  an  hour,  but  in  the  dust  they 
will  live  for  months.  On  slate-pencils,  cups,  glasses, 
or  toys  such  as  children  put  in  their  mouths,  they  will 
live  for  weeks. 

In  the  nose  and  throat  the  bacilli  produce,  by 
their  multiplication  and  by  the  poison  thrown  out  by 
them,  death  of  the  mucous  membrane,  which  appears 
white  and  like  a  membrane.  The  membrane  may  ex- 
tend into  the  nose  or  larynx,  causing  an  obstruction 


CAUSING  ACUTE  INFECTIONS. 


87 


to  breathing.  By  far  the  greater  damage  is  caused 
by  the  poisons  that  are  absorbed  and  affect  the  vari- 
ous organs  and  tissues,  particularly  the  muscle  of  the 
heart,  the  kidneys,  and  the  nervous  system.  The 


Fig.  10.— Bacillus  diphtheriae.     X  1000.     (Drawing 
by  E.  L.  Oatman,  M.D.) 

effect  of  the  poisons  upon  the  heart  results  sometimes 
in  sudden  death,  following  even  slight  exertion  like 
sitting  up  in  bed.  Paralysis  may  follow  diphtheria 
when  the  nervous  system  has  been  attacked. 

Diphtheria  in  the  throat  and  nose  is  detected  by 
finding  the  bacilli  in  the  wipings  made  from  the  mem- 


88  BACTERIOLOGY. 

Diagnosis  brane.  It  is  not  safe  to  rely  solely  upon  the  presence 
and  appearance  of  a  membrane,  because  membranes 
may  be  due  to  infection  with  micro-organisms  other 
than  the  diphtheria  bacilli,  such  as  the  staphylococcus 
and  streptococcus.  In  order  to  say  whether  a  mem- 
brane is  due  to  diphtheria  or  not,  a  sterile  cotton  swab 
is  rubbed  over  the  membrane,  and  then  rubbed  on  the 
surface  of  a  tube  containing  coagulated  blood-serum. 
The  tube  and  swab  are  now  sent  to  the  laboratory  and 
incubated  at  body  temperature  for  twelve  or  twenty- 
four  hours  in  order  to  allow  the  bacteria  present  to 
multiply.  The  growth  is  now  smeared  on  glass  slides, 
stained,  and  examined  under  the  microscope.  If 
diphtheria  bacilli  are  present  they  can  be  readily 
identified  by  their  appearance. 

the'dteease  The  disease  is  spread  to  others  chiefly  by  means 

of  the  bacilli  thrown  from  the  nose  or  mouth  by 
coughing  and  sneezing.  The  sputum  contains  the 
bacilli  in  large  number.  Indirectly  the  disease  is 
spread  from  the  sputum  by  means  of  clrinking-cups, 
handkerchiefs,  door-knobs,  and  among  children  from 
pencils,  chewing  gum,  toys,  and  other  things  that  are 
handled  and  passed  about.  Cats,  rats,  and  mice  may 
carry  the  infection,  and  flies  may  deposit  it  on  food 
and  milk.  Infected  milk  has  been  the  cause  of  a  num- 
ber of  epidemics. 

Duration  The  most  important  and  first  precaution  to  be 

quarantine  taken  in  limiting  the  spread  of  diphtheria  is  quarantine. 
This  means  the  complete  isolation  of  the  sick  person. 
The  length  of  the  quarantine  cannot  be  determined  by 


CAUSING  ACUTE  INFECTIONS.  89 

the  condition  of  the  patient  or  by  the  appearance  of 
the  throat,  because  it  is  possible  and  frequently  is  so 
that  although  the  patient  is  apparently  well  and  the 
throat  clear,  the  bacilli  of  diphtheria  are  still  there. 
In  order  to  tell  when  the  bacilli  have  disappeared  a 
wiping  of  the  throat  is  made  just  as  described  in 


Fig.  11. — Organisms  of  Vincent's  angina,  showing  spirillum 
and  fusiform  bacillus. 

making  the  diagnosis,  incubated  and  examined.  Two 
such  cultures  free  from  diphtheria  bacilli  are  con- 
sidered sufficient  evidence  that  the  patient  is  no  longer 
able  to  transmit  the  disease  to  others.  Among  healthy 
persons,  particularly  attendants  upon  diphtheria  pa- 
tients, the  bacilli  may  be  carried  in  the  throat  for  long 
periods  of  time  without  causing  any  of  the  symptoms 
of  the  disease.  Such  persons  are  called  carriers,  and 
can  transmit  the  disease  to  others. 


90  BACTERIOLOGY. 

All  discharges  from  the  nose  and  mouth  should 
be  collected  on  paper  napkins  and  burned.  A  paper 
napkin  should  be  held  .over  the  nose  and  mouth  while 
coughing  or  sneezing.  All  bed-linen  and  utensils  used 
by  the  patient  should  be  soaked  in  a  5  per  cent,  solution 
of  carbolic  acid  and  boiled.  The  sickroom,  must  be 
fumigated  and  cleaned  after  the  manner  already 
described  under  Disinfection.  All  well  persons,  in- 
cluding the  nurse,  should  receive  an  immunizing  dose 
of  antitoxin.  Nurses  should  wear  a  gown  to  protect 
the  uniform  and  a  cap  over  the  hair. 

The  curative  property  of  antitoxin  was  discovered 
by  von  Behring  in  1894,  and  is  now  in  universal  use 
for  the  cure  and  prevention  of  diphtheria.  By  the  use 
of  antitoxin  the  fatal  cases  have  been  reduced  to  one- 
quarter  of  those  formerly  resulting  in  death.  In  New 
"  York  from  1895  to  I9I°)  80,000  people  received  im- 
munizing doses  of  antitoxin,  and  out  of  this  number 
only  177,  or  0.2  per  cent.,  contracted  diphtheria,  and 
but  one  of  these  resulted  fatally.  The  immunizing 
dose  protects  from  two  to  six  weeks.  Occasionally  the 
injection  of  antitoxin  is  followed  after  a  few  days  by 
a  feeling  of  malaise,  skin  eruption,  vomiting,  albu- 
minuria,  and  swelling  of  the  lymphatic  glands.  This 
condition  is  due  to  anaphylaxis,  or  an  increased  sus- 
ceptibility on  the  part  of  the  patient  to  certain  con- 
stituents of  the  antitoxin,  probably  the  horse-serum, 
which  contains  the  protective  substance.  A  few  cases 
of  sudden  death  following  the  injection  of  diphtheria 
antitoxin  have  been  attributed  to  anaphylaxis. 


CHAPTER  VIII. 

BACTERIA  CAUSING  CHRONIC  INFECTIONS. 

THE  BACILLUS  OF  TUBERCULOSIS. 

TUBERCULOSIS  is  an  infectious  disease  caused  by 
the  tubercle  bacillus,  which  was  discovered  by  Profes- 
sor Koch  in  1882.  The  organism  is  widely  dis- 
tributed over  the  world,  and  is  pathogenic  for  the 
lower  animals  as  well  as  for  man.  It  is  frequently 
found  in  cattle,  less  often  in  goats  and  swine,  rarely  in 
sheep,  horses,  dogs,  and  cats. 

The  bacillus  is  a  slender  rod,  slightly  curved,  with 
rounded  ends.  It  is  purely  parasitic,  that  is,  it  will  not 
grow  or  multiply  outside  a  host.  It  is  never  found 
save  in  the  bodies  and  discharges  of  animals  affected 
by  the  disease,  or  in  the  dust  or  upon  articles  which 
the  discharges  have  contaminated.  It  is  not  motile, 
does  not  form  spores,  and  is  cultivated  on  artificial 
culture  media  with  difficulty.  It  cannot  grow  with- 
out a  liberal  supply  of  oxygen,  and  only  at  body  tem- 
perature. It  is  killed  by  moist  heat  at  70°  C.  in  ten 
minutes,  but  dry  heat  at  100°  C.  requires  one  hour. 
Direct  sunlight  destroys  them  in  two  hours,  but  when 
protected  from  sunlight  they  can  live  for  a  year. 

There  are  four  kinds  of  tubercle  bacilli:  the 
human;  the  bovine,  chiefly  found  in  cattle;  the  avian, 
found  in  birds,  and  the  reptilian.  The  human  tubercle 

(91) 


92  BACTERIOLOGY. 

bacillus  is  only  slightly  infectious  for  cattle,  but  the 
bovine  bacillus  is  infectious  for  human  beings,  par- 
ticularly young  children,  who  may  become  infected 
from  the  milk  of  tuberculous  cattle. 

staining  The  tubercle  bacillus  does  not  stain  readily,  but 

once  stained  it  is  difficult  to  decolorize  it  with  acids. 
For  this  reason  it  is  said  to  be  acid-fast.  The  method 
employed  in  staining  is  as  follows:  The  suspected 
material  is  spread  thinly  on  a  glass  slide  and  dried. 
The  preparation  is  then  covered  with  fuchsin,  a  red 
dye  to  which  has  been  added  a  small  amount  of  car- 
bolic acid  solution  and  steamed,  the  heat  quickening 
the  staining.  Then  the  preparation  is  washed  off  in 
water  and  decolorized  with  a  5  per  cent,  solution  of 
nitric  acid.  This  is  allowed  to  act  until  all  the  red 
color  is  removed.  After  washing  again  in  water  the 
preparation  is  again  stained  with  a  methylene-blue 
solution.  The  picture  produced  by  this  method  shows 
the  tubercle  bacilli  unaffected  by  the  acid  decolorizer 
and  stained  red,  while  all  other  organisms  are  stained 
blue.  In  this  way  the  tubercle  bacillus  may  be  de- 
tected in  discharges  from  suspected  cases. 

Tubercle  In  collecting  urine  for  examination  for  tubercle 

bacilli  in  t        M 

urine  bacilli  it  is  important  to  know  that  the  smegma  bacil- 
lus, a  non-pathogenic  organism  found  in  the  secre- 
tions about  the  genitalia,  possess  the  same  staining 
peculiarities  as  the  tubercle  bacillus ;  so  that  great  care 
must  be  used  to  exclude  it  from  the  urine  by  careful 
cleansing  of  the  external  genitalia  and  collection  of 
the  urine  by  catheter.  In  fluids  like  urine,  pleural  effu- 


CAUSING  CHRONIC  INFECTIONS.  93 

sions  and  ascitic  fluid  the  number  of  tubercle  bacilli 
is  always  small;  so  to  detect  them  the  inoculation  of  Exudates 
guinea-pigs  with  the  fluid  is  often  practised.  If 
tubercle  bacilli  are  present  in  the  fluid  injected,  the  dis- 
ease develops  in  the  animal  after  a  period  of  three  to 
six  weeks. 

The  tubercle  bacillus  may  cause  infection  by 
entering  the  body  in  the  following  ways : — 

Hereditary  transmission,  long  believed  to  be  a 
common  occurrence,  has  not  been  proven  among 
human  beings.  In  very  rare  instances  the  bacilli  may 
pass  from  the  mother  to  the  child  in  the  uterus,  but 
this  depends  upon  some  injury  or  disease  of  the 
placenta. 

Respiratory:  This  is  the  most  common  way  that 
infection  takes  place.  The  sputum  of  consumptives  is 
the  direct  carrier  of  the  infection.  Deposited  in 
houses,  on  floors  and  streets,  the  bacilli  become  incor- 
porated with  the  dust  which  is  breathed  in  by  those  in 
close  contact  with  the  patients.  The  careless  disposal 
of  sputum  is  responsible  for  the  greatest  number  of 
infections. 

Intestinal :  This  is  more  common  in  children  than 
in  adults.  The  bacilli  gain  entrance  through  the  milk 
from  tuberculous  cattle  or  food  infected  by  consump- 
tive people.  The  habit  children  have  o>f  putting  every- 
thing into  their  mouths,  is  responsible  for  many  in- 
fections, particularly  in  houses  where  consumptives 
are  living.  The  bacilli  resist  the  action  of  the  acid  in 
the  stomach,  and  in  the  intestine  may  penetrate  the 


94  BACTERIOLOGY. 

wall  and  lodge  in  the  mesenteric  glands.  From  this 
point  they  may  be  carried  to  remote  tissues  or  organs. 
Cutaneous:  The  bacilli  may  enter  the  skin 
through  injuries  or  abrasions,  giving  rise  to  the  dis- 
ease known  as  lupus  vulgaris. 

Tubercles  Once  in  the  body,  the  tubercle  bacilli  may  become 

localized  in  any  tissue  or  organ,  and  there  proceed  to 
multiply.  The  result  is  the  formation  of  a  nodule  or 
tubercle,  from  which  the  disease  takes  its  name.  The 
tubercles  are  about  the  size  of  a  millet-seed,  and  at 
first  are  distributed  separately  in  an  organ.  As  they 
grow  larger  the  central  portion  is  poorly  supplied  with 
blood,  so  that  it  degenerates,  softens,  becomes  cheesy, 
and  finally  may  ulcerate.  Tubercles  that  are  placed 
close  together  may  coalesce  and  go  on  to  ulceration, 
causing  large  abscesses.  If  the  tubercle  bacilli  reach 
the  circulating  blood  they  may  be  carried  to  many 
organs  and  tissues,  at  once  causing  a  tuberculous  sep- 
ticemia  or  miliary  tuberculosis.  In  such  cases  at 
autopsy  the  miliary  tubercles  are  found  everywhere  in 
the  body. 

It  is  well  to  distinguish  between  the  words  "tuber- 
cular" and  "tuberculous,"  as  they  are  often  used  in- 
correctly. The  word  tubercular  means  nodular  and 
has  no  reference  to  the  nature  or  cause  of  the  nodule. 
Tuberculous,  on  the  other  hand,  is  an  adjective  used 
to  indicate  tissues  infected  with  tubercle  bacilli. 

Toxins  The  damage  done  in  tuberculosis  is  due  almost 

entirely  to  the  absorption  of  the  toxins  fo'rmed  by  the 
tubercle  bacillus.  These  are  of  two  kinds:  an  extra- 


CAUSING  CHRONIC  INFECTIONS.  95 

cellular  or  soluble  toxin,  to  which  is  attributed  the 
fever,  headache,  loss  of  appetite,  and  so  on,  and  an 
endotoxin  which  causes  the  irritation  of  the  tissues 
leading  to  the  formation  of  the  tubercle.  The  ab- 
sorption of  these  toxins  causes  the  formation  of  anti- 
bodies, but  not  in  sufficient  amount  to  cause  immunity. 
The  toxins  of  the  tubercle  bacilli  may  be  obtained  from 
cultures,  and  are  used  under  the  name  of  tuberculin 
in  the  diagnosis  and  treatment  of  the  disease.  The  Tuber. 
tuberculin  reaction  used  in  the  diagnosis  is  based  upon 
an  observation  made  by  Professor  Koch,  that  animals 
having  tuberculosis  were  very  sensitive  to  the  poison, 
and  when  injected  with  even  a  small  amount  of  tuber- 
culin developed  fever,  headache,  nausea,  vomiting,  and 
general  malaise,  while  the  diseased  tissues  became 
temporarily  more  inflamed.  Healthy  animals  were 
unaffected.  This  method  has  been  employed  among 
tuberculous  patients,  using  from  i  to  10  milligrams  of 
the  tuberculin.  Simpler  methods  have  more  recently 
been  used,  such  as  the  von  Pirquet  test,  in  which  the 
tuberculin  is  introduced  into  the  superficial  layers  of 
the  skin  with  a  scarifier,  and  the  Moro  test,  in  which 
the  tuberculin  is  rubbed  in,  in  the  form  of  an  ointment. 
In  the  first  method  a  positive  reaction  is  manifested  by 
fever,  headache,  and  so  on,  as  described  above,  but  in 
the  cutaneous  tests  there  is  only  a  local  redness  about 
the  point  of  inoculation.  A  positive  test  means  that 
tuberculosis  is  present  in  the  body,  but  it  do^s  not  tell 
us  where  or  whether  it  is  active  or  not.  In  children, 
a  positive  reaction  usually  means  active  disease. 


96 


BACTERIOLOGY. 


Tuber- 
culin 


Public 
Health 
measures 
adopted 
in   the 
crusade 
against 
tubercu- 
losis 


Tuberculin  administered  in  increasing  doses,  too 
treatment  small  to<  cause  a  reaction  and  at  fixed  intervals,  de- 
velops a  tolerance  for  the  poison,  and  so  an  immunity. 
This  method  of  treatment  is  being  widely  used,  and 
while  the  results  are  not  prompt,  the  consensus  of 
opinion  is  that  it  exerts  a  beneficial  effect  on  the  course 
of  the  disease. 

During  the  last  ten  years  great  efforts  have  been 
made  to  check  the  ravages  of  this  disease;  in  fact,  a 
crusade  has  been  carried  on  that  has  become  world- 
wide. Among  the  measures  that  have  been  advocated 
are  the  registration  of  all  cases  of  tuberculosis  by 
departments  of  health,  the  establishment  of  institu- 
tions sufficient  to  care  for  the  advanced  cases,  dispen- 
saries where  suspected  cases  may  be  examined  and  sub- 
sequently visited  by  nurses  who  instruct  the  sick  in  the 
proper  way  to  disinfect  the  sputum,  stools,  and  urine, 
and  the  disinfection  of  all  houses  occupied  by  tuber- 
culous patients  before  being  reoccupied.  More  gen- 
eral measures,  such  as  better  sanitary  conditions  in 
factories,  schools,  and  dwellings,  have  been  brought  to 
the  attention  of  the  public,  and  have  created  a  public 
sentiment  that  is  now  bearing  fruit.  As  a  result  of 
this  crusade,  it  is  not  too  much  to  expect  that  the 
death  rate  from  tuberculosis  will  be  materially  reduced, 
and  that  the  spread  of  the  disease  will  be  checked. 

THE  BACILLUS  OF  LEPROSY. 

The  bacillus  causing  leprosy  was  found  by  Han- 
sen,  a  Norwegian,  in  1871,  in  the  nodules  of  leprous 


CAUSING  CHRONIC  INFECTIONS.  97 

patients.  It  is  a  short  rod  about  the  size  of  the  tubercle 
bacillus,  which  it  resembles  closely  both  in  appearance 
and  in  staining  peculiarities.  It  takes  stains  with  diffi- 
culty, but  once  stained  it  resists  decolorizing  with 
acids.  For  this  reason  it  is  spoken  of  as  being  acid- 
fast.  It  is  very  difficult  to  cultivate  on  the  culture 
media  at  our  disposal.  Efforts  to  transmit  the  disease 
to  animals  have  not  been  successful. 

Leprosy  is  one  of  the  oldest  diseases  known,  and  Distribu. 
Dr.  Osier  says  it  existed  in  Egypt  three  or  four  thou-  thendisf- 
sand  years  before  Christ.  It  is  referred  to  many  times 
in  the  Bible,  but  there  is  reason  to  believe  that  other 
diseases  were  included  under  the  same  name.  The  dis- 
ease has  continued  to  exist  to  the  present  time,  but  was 
particularly  prevalent  in  the  Middle  Ages.  At  pres- 
ent it  exists  in  Iceland,  Norway,  Sweden,  Russia, 
Spain,  Portugal,  England,  West  Indies,  China,  India, 
and  the  Philippines.  In  the  United  States  small  num- 
bers of  cases  are  to  be  found  in  Louisiana,  Minnesota, 
Florida,  and  Texas,  with  isolated  cases  widely 
scattered. 

The  disease  manifests  itself  either  as  tubercular 
leprosy  or  as  anesthetic  leprosy.  In  the  former, 
nodules  develop  in  the  skin  which  soften  and  finally 
form  discharging  sores.  In  the  anesthetic  form  the 
nerves  are  principally  affected,  and  this  leads  to  loss 
of  sensation  in  the  skin.  Both  forms  may  exist  at  the 
same  time. 

The  way  that  infection  takes  place  is  not  posi- 
tively known,  but  many  believe  that  it  enters  the  skin 


98  BACTERIOLOGY. 

or  mucous  membranes  through  close  personal  contact. 
While  hereditary  transmission  cannot  be  denied,  no 
instance  has  so  far  been  recorded.  The  infectious 
material  is  found  in  the  discharges  from  the  open 
sores,  in  the  urine,  milk,  blood,  sputum,  and  nasal 
secretions.  The  last  are  especially  infectious. 

The  spread  of  the  disease  is  checked  by  the  seg- 
regation of  the  lepers  in  the  communities  where  the 
disease  prevails.  Attendants  upon  leprous  patients 
should  know  that  the  disease  is  one  of  the  most  diffi- 
cult to  contract  of  all  the  infectious  diseases,  and  that 
it  is  very  rare  for  nurses  to  be  infected  while  attend- 
ing cases.  Careful  attention  should  be  given  to  dis- 
infecting the  nasal  discharges  and  sputum. 


CHAPTER  IX. 

THE  DISEASES  CAUSED  BY  THE  MOLDS,  YEASTS, 
AND  HIGHER  BACTERIA. 

REFERRING  back  to  the  classification  of  the  fungi 
given  in  chapter  ii,  there  still  remains  to  be  con- 
sidered the  hyphomycetes,  or  molds,  and  the  blasto- 
mycetes,  or  yeasts.  Under  the  head  of  higher  bacteria 
are  organisms  having  characters  that  make  it  difficult 
to  classify  them  either  as  molds  or  yeasts.  The  most 
important  of  the  diseases  caused  by  the  higher  bac- 
teria is: — 

ACTINOMYCOSIS. 

This  is  an  infection  generally  running  a  chronic 
course,  caused  by  the  actinomyces,  or  ray  fungus.  It 
prevails  chiefly  among  cattle;  but  sheep,  dogs,  cats, 
horses,  and  swine  are  also  susceptible.  It  occasionally 
occurs  in  man. 

The  parasites  can  be  seen  by  the  naked  eye,  in 
pus  from  the  abscesses,  as  minute,  yellow  masses, 
often  called  sulphur  granules.  If  the  granules  are 
examined  under  the  microscope  they  are  found  to  be 
made  up  of  a  central  thick  mass  of  filaments  which 
radiate  at  the  periphery.  It  is  because  of  this  radial 
arrangement  that  the  parasite  is  called  the  ray  fungus. 
The  ends  of  the  filaments  are  often  club-shaped. 

The  infection  is  located  most  often  about  the 

(99) 


100 


BACTERIOLOGY. 


mouth  or  in  the  throat.  It  starts  as  a  nodule,  hard 
at  first,  but  later  undergoes  softening  and  finally  sup- 
purates, causing  a  discharging  sinus.  Infections  of 
the  skin,  lungs,  intestines,  and  appendix  have  been  de- 
scribed. The  parasite  is  supposed  to  enter  the  body 


Fig.  12. — Actinomyces  hominis  (lung).    X  350. 
(Lenhartz-Brooks.) 

in  grain,  oats,  barley,  or  rye,  and  in  cattle  from  hay 
or  straw. 

The  disease  is  not  highly  infectious,  and  all 
danger  is  removed  by  careful  disinfection  of  the  dis- 
charges containing  the  pus. 

YEASTS. 

Yeast-cells  are  much  larger  than  bacteria;  they 
are  oval  in  shape  and  have  a  thick  cell -membrane. 


DISEASES  CAUSED  BY  MOLDS,  ETC  101 

The  protoplasm  contains  vacuoles  and  one  or  more 
nuclei.  The  manner  of  reproduction  is  characteristic; 
the  capsule  protrudes  and  forms  a  bud  and  contains  a 
part  of  the  protoplasm  and  a  half  of  the  nucleus.  It 
gradually  grows  larger,  and  is  eventually  pinched  off 
to  become  another  cell.  The  cells  frequently  contain 
spores,  which  are  liberated  when  the  cell  disintegrates. 
The  most  important  property  of  yeasts  is  the  fer- 
mentation of  sugars  whereby  the  sugar  is  changed 
into  ethyl  alcohol  and  carbon  dioxide.  Commercially 
the  yeasts  are  used  in  a  variety  of  ways,  but  chiefly 
in  the  manufacture  of  beers  and  wines.  Few  of  the 
yeasts  are  infectious  for  man,  and  but  one  will  be 
mentioned. 

BLASTOMYCOSIS. 

This  infectious  disease  is  caused  by  a  yeast  called 
the  blastomyces.  In  appearance  it  corresponds  to  the 
yeast-cells  described  above,  having  a  thick  cell-wall, 
with  one  or  more  nuclei  in  the  protoplasm,  and 
vacuoles.  Occasionally  it  forms  threads  called  mycelia 
(sing,  mycelium). 

The  skin  is  most  often  affected.  Small  nodules 
form,  which  soften  and  discharge  a  yellow  pus.  They 
spread  slowly  and  sometimes  involve  a  considerable 
area  of  skin.  Infection  of  the  lungs  is  more  serious 
and  often  leads  to  pneumonia.  A  few  cases  of  gen- 
eral infection  have  been  reported  with  abscesses  in 
the  liver,  spleen,  and  lungs. 

Where  the  organisms  that  cause  the  disease  come 


102  BACTERIOLOGY. 

from  is  not  known,  but  in  skin  infections  it  is  pre- 
sumed that  they  enter  along  the  hairs  or  through 
small  abrasions.  It  is  not  a  very  infectious  disease, 
and  the  infection  of  others  may  be  prevented  by  dis- 
infecting the  pus  discharged. 


Fig.  13.— Microsporon  furfur.    (After  Lenhartz.) 

MOLDS. 

The  molds  in  their  structure  are  much  more  com- 
plex than  the  yeasts.  They  are  characterized  by  the 
formation  of  mycelial  threads  and  terminal  organs  of 
reproduction  called  hyphse.  They  may  be  seen  grow- 
ing on  decomposing  substances,  and  look  like  little 
pieces  of  cotton.  Of  the  many  kinds  of  molds,  but  a 
few  are  pathogenic  for  man. 


DISEASES  CAUSED  BY  MOLDS,  ETC  103 

THRUSH. 

This  occurs  in  infants  and  young  children,  caus- 
ing sore  mouth.  It  is  caused  by  a  mold  called  the 
Oidium  albicans.  The  mucous  membrane  is  red  and 
dotted  with  small,  white  flakes,  which  contain  the 
organism. 


Fig.  14. — Trichophyton  tonsurans.     (After  Bi 

PITYRIASIS  VERSICOLOR. 

The  infectious  mold  here  is  the  Microsporon 
furfur,  which  lives  on  rather  than  in  the  skin.  It 
produces  yellowish,  scaly  patches  on  the  chest,  back, 
or  abdomen,  which  may  spread  over  large  areas  of 
the  skin.  When  scratched,  the  growth  can  be  re- 
moved in  fine  scales  which  contain  the  mold.  It 
affects  chiefly  the  uncleanly. 

FAVUS. 

The  mold  causing  favus  is  called  the  Achorion 
Schonleini,  after  its  discoverer.  It  attacks  the  hair-fol- 


104  BACTERIOLOGY. 

licles,  especially  of  the  scalp,  and  forms  yellow  crusts 
about  the  base  of  the  hairs.  If  the  crusts  are  re- 
moved and  examined  under  the  microscope,  the  para- 
sites can  be  found  in  them.  The  disease  is  very 
resistant  to  treatment. 

RINGWORM. 

This  is  a  very  common  affection  among  children, 
and  is  caused  by  the  Tinea  trichophyton.  There  are 
three  types  of  the  parasite:  the  Tinea  tonsurans, 
which  attacks  the  hairs  of  the  scalp ;  the  Tinea  sycosis, 
which  attacks  the  hairs  of  the  bearded  part  of  the 
face,  and  the  Tinea  circinata,  which  attacks  the  skin. 
It  starts  as  a  slightly  elevated,  scaly  spot,  which 
gradually  widens,  forming  a  red,  scaly  patch,  with 
raised  edges.  The  hairs  invaded  by  the  parasites 
break  off  and  leave  the  center  devoid  of  hair.  The 
disease  spreads  from  one  person  to  another  by  direct 
contact. 


CHAPTER  X. 

THE  BACTERIA  IN  WATER  AND  MILK. 

THE  BACTERIA  IN  MILK. 

FROM  its  appearance  and  taste  little  can  be  known 
of  the  bacterial  content  of  milk.  It  may  be  teeming 
with  bacteria,  yet  give  no  indication  of  their  presence. 
In  fact,  ordinary  market  milk  contains  from  100,000 
to  1,000,000  bacteria  in  every  cubic  centimeter. 

How  do  these  bacteria  get  into  the  milk?  In  the 
udder  of  the  healthy  cow  the  milk  is  practically  free 
from  bacteria,  but  they  live  in  the  milk-ducts  in  the 
teats,  and  get  into  the  milk  as  it  is  drawn.  The  chief 
source  of  bacteria  in  milk  lies  in  the  uncleanly  methods 
o>f  collecting  it.  Many  get  in  from  the  dust-laden  air  of 
the  cow-stable,  from  the  dirt  on  the  hide  of  the  cow, 
unclean  milk-pails,  and  from  the  dirty  hands  of  the 
milkers.  It  is  a  true  saying  that  the  number  of  bac- 
teria in  milk  is  an  index  of  the  cleanliness  with  which 
it  has  been  collected.  Once  in  the  milk,  the  bacteria 
multiply  with  great  rapidity,  for  milk  is  an  excellent 
medium  for  the  cultivation  of  bacteria.  The  tempera- 
ture of  the  milk  for  some  time  after  it  is  drawn  also 
favors  their  development. 

To  prevent  the  contamination  of  milk  with  ex- 

1  r  .  tion    of 

cessive  numbers  of  bacteria,   all  that   is   required  is     contam- 
ination 
cleanliness, — clean  stables,  clean  cattle,  milkers  with 

(105) 


106  BACTERIOLOGY. 

clean  hands,  and  clean  milk-pails.  Immediately  after 
the  milk  is  drawn,  it  should  be  cooled  to  5°  C.  (40°  F.) 
and  kept  at  this  temperature  until  sold. 

PStion"  On  account  of  the  difficulty  in  maintaining  strict 

supervision  over  the  milk-supply  in  cities  where  the 
milk  is  collected  from  a  wide  area,  we  have  come  to 
the  conclusion  that  pasteurization  is  essential  to  render 
the  supply  safe  for  use,  particularly  in  infant  feeding. 
Pasteurization  is  accomplished  by  heating  the  milk  to 
60°  C.  (140°  F.)  for  twenty  minutes  or  65°  C. 
(158°  F.)  for  fifteen  minutes.  The  milk  is  imme- 
diately cooled  to  5°  C.  (40°  F.)  and  kept  at  this  tem- 
perature till  used.  Milk  to  be  used  in  feeding  infants 
should  be  modified  and  poured  into  the  nursing  bottles 
before  being  pasteurized.  It  should  be  used  within 
twenty-four  hours.  The  pasteurization  kills  all  the 
bacteria,  but  not  the  spores.  If  the  milk  is  cooled  as 
directed,  the  spores  will  not  develop. 

The  bacteria  usually  present  in  milk  are  harmless 
in  so  far  as  they  are  able  to  produce  specific  disease; 
but  while  they  may  be  considered  as  harmless  for 
healthy  adults,  they  may  be  very  dangerous  for  in- 
fants and  sick  persons.  The  great  loss  of  life  among 
infants  under  2  years  of  age  from  intestinal  or  diar- 
rheal  diseases  show  this.  During  the  summer  months, 
when  the  number  o-f  bacteria  is  more  than  at  any  other 
time  of  the  year,  the  milk  undergoes  chemical  changes 
which  lead  to  disturbances  in  digestion  and  infection  of 
the  intestines. 

Diseases  other  than  these  caused  by  the  ordinary 


BACTERIA  IN  WATER  AND  MILK.  107 

dirt  bacteria  may  be  spread  in  milk.     Many  epidemics    Diseases 

: ,    .  ......      transmitted 

of  scarlet  fever,  typhoid  fever,  measles,  and  diphtheria     by  miik 
have  been  traced  to  infected  milk.     The  infection  is 
introduced  into'  the  milk  at  the  dairy,  usually  by  some- 
one sick  with  the  disease  in  question. 

The  transmission  of  tuberculosis  in  the  milk  from 
tuberculous  cattle  is  believed  to  be  of  common  occur- 
rence, particularly  among  infants.  The  tubercle  bacilli 
may  pass  through  the  walls  of  the  intestine  without 
causing  any  disease  of  the  intestinal  wall  itself,  and 
lodge  in  the  mesenteric  lymphatic  glands.  They  may 
lie  dormant  for  years  and  later  on,  when  the  resistance 
is  lowered  by  disease  or  by  unsanitary  conditions  of 
living,  become  active  and  cause  tuberculosis  in  what- 
ever organ  or  tissue  they  may  have  lodged.  The  milk 
from  cattle  having  tuberculosis  of  the  udder  is  the 
most  dangerous;  but  even  when  the  udder  is  healthy 
and  the  disease  located  in  other  organs,  the  milk  may 
contain  tubercle  bacilli.  Not  only  is  the  milk  from 
tuberculous  cattle  infectious,  but  also  the  products — 
butter  and  cheese — made  from  the  milk.  From  what 
has  been  said,  it  is  easy  to-  see  the  danger  of  using  raw 
cows'  milk  for  infant  feeding  without  positive  assur- 
ance that  the  cows  have  been  tuberculin  tested  and  are 
free  from  tuberculosis. 

THE  BACTERIA  IN  WATER. 

Water  as  it  falls  in  the  form  of  rain  is  free  from 
bacteria.  It  begins  to  be  contaminated  with  bacteria 
when  it  reaches  the  dust-laden  air  above  the  earth,  and 


108  BACTERIOLOGY. 

after  it  reaches  the  ground  the  number  of  bacteria  is 
greatly  increased  from  the  soil.  As  it  drains  from  the 
surface  of  the  earth  or  percolates  through  it,  it  is 
classed  either  as  surface  water,  of  which  ponds,  lakes, 
or  rivers  are  examples,  or  as  ground  water,  which 
feeds  wells.  Surface  water  always  contains  large 
numbers  of  bacteria,  but  the  water  in  wells  contains 
only  a  few  on  account  of  the  filtering  action  of  the 
soil.  While  the  number  of  bacteria  in  surface  water 
is  large,  there  is  going  on  constantly  processes  of  puri- 
fication which  keep  the  number  in  check. 
Natural  First,  there  is  sedimentation  or  the  sinking  of 

methods  . 

of  pun-     impurities  by  reason  of  their  weight.     The  effect  of 

fication  * 

sedimentation  can  be  seen  after  floods,  where  the  mud 
and  dirt  is  found  over  the  flooded  areas.  Sedimenta- 
tion takes  place  slowly ;  so  in  streams  that  are  flowing 
fast  it  cannot  be  relied  upon  to  remove  much  of  the 
impurities.  Aeration  is  another  factor.  This  means 
the  mixing  of  water  with  air,  as  takes  place,  for  ex- 
ample, in  water-falls.  It  does  not  destroy  the  bacteria 
but  it  removes  objectionable  odors.  Sunlight  exerts  a 
powerful  destructive  action  on  the  bacteria  in  water, 
provided  the  depth  of  the  water  is  not  too  great  for 
the  sunlight  to  penetrate.  Unfortunately,  the  pene- 
trating power  of  sunlight  is  not  great ;  so  its  action  is 
-  limited  to  the  upper  layers  of  the  water.  The  ground 
water  is  purified  by  the  filtering  action  of  the  soil, 
which  is  very  efficient,  provided  the  amount  of  water 
to  be  filtered  is  not  too  great  and  it  is  not  required  to 
work  continuously. 


BACTERIA  IN  WATER  AND  MILK.  109 

The  ordinary  soil  bacteria  in  water  are  harmless. 
It  is  only  the  pathogenic  bacteria  in  the  soil  from 
human  excreta,  like  the  typhoid  and  dysentery  bacilli 
and  the  cholera  spirilla,  that  get  into  the  water  and 
cause  disease.  In  testing  the  water  to  see  whether  it 
can  transmit  these  diseases  or  not,  it  is  almost  useless 
to  look  for  the  disease-producing  bacteria  themselves, 
because  they  are  extremely  difficult  to  find.  The  pres- 
ence of  intestinal  bacteria  is  looked  for,  particularly 
the  colon  bacillus,  and  when  they  are  found  in  large 
numbers  the  water  is  condemned  for  drinking  pur- 
poses: first,  because  drinking-water  should  not  con- 
tain substances  excreted  from  the  intestines  of  man  or 
animals,  and,  secondly,  water  that  does  contain  such 
substances  is  constantly  open  to  infection  with  bacteria 
that  produce  disease. 

Nowadays  practically  all  surface  waters  are  con-    Artificial 

meth  ds  of 

tammated  with  human  sewage.  To  render  these  purification 
waters  safe  for  drinking  purposes  in  cities,  the  natural 
process  of  water  purification  cannot  be  relied  upon,  and 
artificial  methods,  based  on  filtration,  are  employed. 
The  water  may  be  made  to  percolate  through  beds 
made  of  fine  gravel  and  covered  with  a  thick  layer  of 
fine  sand.  The  dirt  and  slime  in  the  water  cling  to 
the  small  particles  of  the  sand,  and  only  the  water  free 
from  its  impurities  is  permitted  to  pass  through. 
About  90  per  cent,  of  the  bacteria  in  water  can  be 
removed  by  sand  filtration.  In  mechanical  filtration, 
a  chemical  substance  like  alum  is  added  to  the  water 
in  sufficient  quantity  to  coagulate  the  solid  and  ex- 


110  BACTERIOLOGY. 

traneous  materials,  which  sink  and  carry  the  bacteria 
with  them.  In  the  home,  water  may  be  rendered  pure 
by  filtration  through  porcelain  filters,  and,  where  these 
are  not  available,  by  boiling.  The  flat  taste  of  boiled 
water  may  be  removed  by  passing  the  water  from  one 
container  to  another  so  that  air  may  be  mixed  with  it. 


CHAPTER  XL 
DISEASES  CAUSED  BY  PROTOZOA. 

IN  the  classification  of  micro-organisms  in  chaj>- 
ter  ii,  they  were  divided  into  two  great  classes, — those 
belonging  to  the  animal  and  those  belonging  to  the 
vegetable  kingdom.  So  far  we  have  studied  only  the 
vegetable  micro-organisms, — the  molds,  yeasts,  and 
bacteria.  The  protozoa  (sing,  protozoon)  represent 
the  lowest  form  o>f  animal  life,  and  are  composed  of  a 
single  cell  made  up  of  a  nucleus  surrounded  by  a  mass 
of  protoplasm.  The  protoplasm  is  concerned  with  the 
nutrition  of  the  cell,  while  the  nucleus  controls  the 
vital  functions,  particularly  reproduction.  Compara- 
tively few  of  the  many  species  of  protozoa  are  known 
to  be  pathogenic  for  man.  The  life  cycle  of  the  pro- 
tozoa is  peculiar  in  that  part  is  lived  inside  the  body 
of  some  animal,  and  part  outside  the  body.  During 
the  cycle  they  may  take  on  various  shapes  and  sizes. 

AMEBIC  DYSENTERY. 

This  is  a  chronic  form  of  dysentery,  frequently 
associated  with  abscess  of  the  liver,  which  is  especially 
prevalent  in  the  tropics;  in  fact,  the  disease  is  some- 
times called  tropical  dysentery.  It  is  found  quite  fre- 
quently in  the  Southern  States  and  occasionally  in  the 
Northern  States.  It  is  caused  by  the  Ameba  histo- 

(111) 


112  BACTERIOLOGY. 

lytica,  a  protozoan  parasite,  larger  than  any  of  the  bac- 
teria that  have  been  studied.  It  is  composed  of  an 
outer  clear  zone,  a  granular  inner  zone  which  contains 
the  nucleus,  and  a  cavity  called  a  vacuole.  It  moves 
by  extending  a  portion  of  the  outer  clear  zone,  called 
a  pseudopod,  into  which  the  rest  of  the  cell  body  flows. 
The  pseudopods  may  also  embrace  small  particles  of 
food  and  make  them  part  of  their  bodies.  The  amebse 
are  very  sensitive  to  changes  in  temperature,  and 
motility  can  be  seen  only  at  body  temperature.  Repro- 
duction takes  place  either  by  simple  division  or  by  the 
formation  of  smaller  cells  called  daughter-cells,  which 
are  set  free  and  develop  into  parasites. 

The  infection  with  amebse  comes  from  drinking 
infected  water  and  possibly  from  eating  uncooked 
vegetables  that  have  been  washed  in  infected  water. 
After  being  ingested  the  amebee  lodge  in  the  intestine 
and  cause  inflammatory  changes  that  lead  to  ulcera- 
tion.  It  is  not  uncommon  for  the  amebse  to  be  carried 
from  the  intestine  to  the  liver,  where  they  may  cause 
abscesses.  The  stools  contain  the  amebee  and,  to  pre- 
vent the  disease  from  spreading,  the  stools  must  be  dis- 
infected with  5  per  cent,  solution  of  carbolic  acid.  In 
countries  where  the  disease  prevails,  all  water  used  for 
drinking  purposes  should  be  boiled,  and  no  uncooked 
vegetables  eaten  unless  washed  in  boiled  water. 

The  diagnosis  of  amebic  dysentery  is  made  by 
finding  the  amebae  in  the  stools.  This  can  be  done  by 
examining  under  the  microscope  the  mucus  or  pus  in 
the  stool  or  that  obtained  by  passing  a  rectal  tube  high 


DISEASES  CAUSED  BY  PROTOZOA. 


113 


into  the  bowel.  The  material  to  be  examined  must  be 
kept  warm  in  order  to  preserve  the  motility  of  the 
amebae. 

The  disease  is  of  long  duration  and  no  specific 
method  of  treatment  is  known.  The  drug  emetin  has 
been  used  much  of  late,  with  success. 


Fig.  15. — Ameba  coli.    From  dysenteric  stool.     (Zeiss  Apochr., 
1 ;  oil  immersion,  H2-)      (After  Losch.) 

SYPHILIS. 

The  Treponema  pallidum-  is  the  infectious  agent 
causing  syphilis.  It  was  discovered  in  1905.  It  is  a 
very  delicate  spiral  with  from  3  to  12  turns  and  with 
pointed  ends.  The  cultivation  of  the  organism  was 
not  successful  until  1911,  when  Dr.  Noguchi,  at  the 
Rockefeller  Institute  in  New  York,  found  that  they 


1 14  BACTERIOLOGY, 

i-  would  grow  only  when  all  oxygen  was  excluded  and 

osv 

fresh  tissue  of  the  kidney  or  liver  was  added  to  the 
culture  media.  These  spiral  organisms,  or  spirochetes, 
as  they  are  sometimes  called,  are  actively  motile  and 
stain  with  difficulty.  They  can  be  found  in  all  dis- 
eased organs  and  tissues  in  the  earlier  stages  of  the 
disease,  but  not  always  in  the  later  stages.  They  are 
readily  destroyed  by  drying,  and  are  killed  by  the 
ordinary  disinfectant  solutions  such  as  bichloride  of 
mercury  i :  1000  and  carbolic  acid  5  per  cent. 
Path  of  The  infection  takes  place  through  small  injuries 

infection 

or  cracks  in  the  skin  or  mucous  membranes,  and  is 
spread,  in  the  vast  majority  of  cases,  through  sexual 
intercourse.  On  this  account  syphilis  has  been  termed 
a  venereal  disease.  It  is  quite  possible  to  become 
infected  in  other  ways.  People  with  syphilitic  sores 
in  the  mouth  may  transmit  the  infection  to  others  by 
kissing  or  from  drinking-glasses  or  eating-utensils 
that  they  have  used.  Wet-nurses  may  become  infected 
by  nursing  a  child  that  is  infected.  Physicians  may 
become  infected  in  the  performance  of  professional 
duties,  as  in  the  examining  of  patients  and  in  the 
attendance  of  women  in  confinement.  Nurses  can  be 
infected  from  the  sores  of  patients  under  their  care. 
This  kind  of  infection  is,  fortunately,  not  very  com- 
mon, and  may  be  prevented  entirely  by  careful  disin- 
fection of  the  hands  after  attending  such  cases,  or  by 
the  use  of  rubber  gloves.  Children  may  be  infected 
in  the  uterus  or,  during  labor,  from  sores  in  vagina. 
Infection  manifests  itself  first  by  a  sore  called  a 


Fig.  16. — Treponema  pallidum  in  smear  from  secretion  of  a 
fresh,  hard  chancre.  The  dark  spots  represent  the  red  blood- 
cells;  the  light,  wavy  lines  the  spirochetes.  X  1000.  (After 
Lenharts.} 

result  is  a  general  skin  eruption,  sore  throat,  fever, 
and  anemia, — symptoms  that  develop  in  from  six  to 
twelve  weeks  after  the  chancre,  and  mark  the  begin- 
ning of  the  secondary  stage.  The  disease  is  most 
infectious  at  this  period.  Later  the  spirochetes  be- 
come localized  in  certain  tissues,  particularly  the  brain 
and  spinal  cord,  and  lead  to  the  formation  of  nodules 


DISEASES  CAUSED  BY  PROTOZOA.  115 

chancre,  which  develops  from  three  to  six  weeks  after 
exposure.  It  may  be  located  anywhere  on  the  body, 
but  is  always  at  the  point  where  infection  entered. 
The  organisms  are  at  first  localized  in  the  primary 
sore,  but  very  soon  spread  to  the  glands  near  by,  and 
then  to  the  blood,  causing  a  general  infection.  The 


116  BACTERIOLOGY. 

which  have  a  tendency  to  become  soft  and  cheesy.  A 
nodule  of  this  sort  is  called  a  gumma  and  is  character- 
istic of  the  tertiary  stage  of  syphilis. 

Diagnosis  The   presence   of    syphilis   may   be    detected    by 

examining  the  serum  from'  the  sores  for  spirochetes. 
This  is  done  by  mixing  the  serum  with  a  drop  of  india- 
ink,  which  makes  the  colorless  spirochetes  easier  to 
see.  A  better  method,  and  one  now  in  general  use, 
is  the  Wassermann  reaction,  which  aims  to  detect  the 
presence  of  the  immune  substances  that  develop  in  the 
blood  soon  after  infection  has  taken  place.  The 
technique  of  the  reaction  is  complicated  and  will  not 
be  taken  up  here;  suffice  it  to  say  that  it  is  successful 
in  from  90  to  95  per  cent,  of  the  cases. 

Killed  cultures  of  the  spirochetes  may  also  be 


utilized  in  diagnosis  by  injecting  a  very  small  amount 
of  the  culture  into  the  superficial  layers  of  the  skin. 
This  is  called  the  luetin  test,  and  was  devised  by  Dr. 
Noguchi.  A  successful  or  positive  test  is  shown  by 
the  development  of  a  hard,  inflamed  nodule  at  the 
point  of  injection,  and  is  due  to  the  hypersensitiveness 
of  the  skin  to  the  syphilitic  poison.  The  test  is  of  value 
only  in  the  later  stages  of  the  disease. 

THE  SPIROCHETE  OF  RELAPSING  FEVER. 

The  cause  of  relapsing  fever  is  a  group  of  spiro- 
chetes, the  individual  members  of  which  differ  in 
minor  details  in  the  various  countries  where  the  dis- 
ease prevails.  The  spirochetes  are  long,  delicate 


DISEASES  CAUSED  BY  PROTOZOA.  117 

threads  with  4  to  10  spirals  and  I  flagellum  which 
propels  them  about  actively.  They  can  be  found  in 
the  blood  of  those  sick  with  the  fever.  At  present  the 
infection  is  most  widespread  in  India  and  Africa,  but 
sixty  to  seventy  years  ago  epidemics  occurred  in  this 
country. 

People  infected  with  the  spirochetes  develop  a 
fever  of  relapsing  type.  First  there  is  a  period  of 
fever  lasting  five  to  seven  days,  then  a  period  of  re- 
mission of  the  same  -duration.  It  is  spread  by  insects 
or  ticks  which  become  infected  by  sucking  the  blood 
of  patients  having  the  disease.  One  attack  usually 
confers  immunity. 

In  preventing  the  spread  of  the  disease  it  is  im- 
portant to  isolate  the  patient  and  disinfect  the  bedding, 
clothing,  and  apartments.  Particular  attention  should 
be  given  to  the  extermination  of  bedbugs. 

VINCENT'S  ANGINA. 

This  is  an  infectious  disease  of  the  gums,  mouth, 
or  throat,  characterized  either  by  the  formation  of  a 
membrane  which  may  be  identical  with  the  diphtheritic 
membrane,  or  by  ulcerations  which  have  a  punched- 
out  appearance.  In  smears  made  from  the  membrane 
or  ulcers,  large,  fusiform  bacilli,  broad  in  the  middle, 
with  tapering  ends  and  long  spirilla,  are  constantly 
found  and  are  supposed  to  be  the  cause  of  the  infection. 
It  is  the  belief  now  that  the  spirilla  are  but  a  later 
stage  in  the  development  of  the  fusiform  bacilli.  As 


118  BACTERIOLOGY. 

both  forms  are  difficult  to  cultivate,  the  diagnosis  must 
be  made  by  examining  smears  made  directly  from  the 
throat.  These  organisms  may  be  present  with  the 
bacilli  of  true  diphtheria,  and  are  said  to  aggravate 
the  infection.  (See  Fig.  n,  page  89.) 

The  disease  is  usually  mild  and  responds  fairly 
promptly  to  local  treatment,  but  in  some  cases  where 
the  nature  of  the  infection  has  not  been  recognized  and 
properly  treated,  the  ulceration  and  destruction  of 
tissue  in  the  throat  may  be  extensive.  It  is  spread 
directly  from  person  to  person  through  the  secretions 
from  the  mouth.  The  danger  o>f  becoming  infected 
is  not  great. 

MALARIAL  FEVER. 

Malarial  fever  is  an  acute  infection  caused  by  a 
protozoan  parasite.  It  is  characterized  by  intermit- 
tent chills  and  fever  and  sweats,  and  accompanied  by 
anemia.  There  are  three  types  of  the  fever  caused  by 
three  species  of  the  parasite :  the  tertian  type,  with 
chill  and  fever  every  third  day;  the  quartan,  with 
chill  and  fever  every  fourth  day;  and  the  estivo- 
autumnal,  with  an  irregular  fever  like  typhoid. 

The  disease  is  transmitted  from  one  person 
to  another  by  the  female  mosquito  of  the  genus 
Anopheles.  They  can  be  distinguished  from  the  ordi- 
nary mosquito,  the  Culex,  by  their  position  when  they 
alight.  The  body  of  the  Culex  is  always  parallel  to 
the  surface,  while  the  body  of  the  Anopheles  forms  a 
sharp  angle  with  it.  When  the  Anopheles  feeds  on 


DISEASES  CAUSED  BY  PROTOZOA. 


119 


infected  blood  the  malarial  parasites  are  taken  into 
the  stomach  and  undergo  reproduction.  After  seven 
to  ten  days  they  find  their  way  to  the  salivary  glands. 
When  the  mosquito  bites  man  the  parasites  are  ex- 
creted with  the  saliva  into-  the  wound.  In  the  blood 
the  parasites  enter  and  develop  within  the  red  blood- 
cells.  As  they  grow  they  fill  more  and  more  of  the 
corpuscle  and  finally  become  segmented  into  smaller 


Fig.  17. — Plasmodium  vivax,  parasite  of  tertian  fever.  In  the 
upper  row  and  on  left  of  lower  row,  various  stages  of  intra- 
corpuscular  development ;  the  two  last  figures  in  lower  row  are 
free  sexual  individulas,  microgametocytes  (sperm  cells),  which 
are  about  to  set  free  the  microgametes,  or  males.  (After 
Reinhardt.) 

bodies  that  are  to  become  parasites.  When  this  de- 
velopment is  complete,  requiring  forty-eight  or  seventy- 
two  hours,  depending  upon  the  type  of  parasite,  the 
red  blood-corpuscle  is  ruptured  and  the  segments  set 
free  in  the  circulating  blood,  causing  the  chill  and 
fever  that  are  so  characteristic  of  the  disease.  In  this 
way  more  and  more  blood-cells  are  attacked  and 
destroyed,  which  explains  the  anemia. 


120  BACTERIOLOGY. 

The  diagnosis  is  made  by  finding  the  parasites 
in  the  blood.  They  can  be  found  by  examining  either 
fresh  preparations  or  stained  specimens.  In  the  for-- 
mer  the  parasites  can  be  seen  inside  the  red  blood- 
corpuscles  as  colorless  bodies  containing  granules  of 
pigment  that  are  in  active  motion.  In  the  stained 
specimens  the  parasites  are  motionless,  but  are  much 
more  distinctly  seen. 

The  spread  of  malaria  is  controlled  by  all  meas- 
ures that  aim  at  the  extermination  O'f  the  mosquito. 
As  the  mosquito  lives  and  breeds  in  swamps  and  ponds, 
attention  should  be  directed  to  these  places  first.  The 
larvae  from  which  the  mosquito  develops  live  and  grow 
near  the  surface  of  stagnant  water.  If  oil  is  spread 
on  the  water  the  larvae  cannot  hatch  out  into  mos- 
quitoes. Swamps,  when  it  is  practical  to  do  so,  should 
be  drained  or  filled  in.  In  districts  where  malaria  is 
known  to  exist,  the  house  should  be  screened. 

TRYPANOSOMES. 

A  trypanosome  is  a  long  micro-organism,  with 
spirally  twisted  body.  On  one  side  is  a  membrane  the 
edge  of  which  is  cord-like  and  extends  beyond  the  body 
to  form  a  whip  or  flagellum.  The  wave-like  move- 
ments of  the  membrane  and  the  movements  of  the 
flagellum  propel  the  trypanosome  about.  The  proto- 
plasm is  granular  and  contains  two  nuclei.  Reproduc- 
tion takes  place  by  a  longitudinal  splitting  of  the 
whole  cell  body.  The  life  cycle  is  not  clear,  but  in 


DISEASES  CAUSED  BY  PROTOZOA.  121 

some  species  at  least  there  is  development  in  an  inter- 
mediate host,  generally  some  species  of  fly. 

There  are  about  60  species  of  trypanosomes,  many 
of  which  are  pathogenic  for  animals,  but  only  2  are 
known  to*  cause  disease  in  man.  The  Trypanosoma 
gambiense  is  the  cause  of  the  sleeping  sickness,  a  dis- 
ease prevalent  in  equatorial  Africa.  One  of  the 
natural  hosts  of  the  parasite  is  the  crocodile,  and  a 
species  of  fly,  the  Glossura  palpales,  that  feeds  on  the 
blood  of  these  animals,  transmits  the  infection  to 
human  beings.  Trypanosomiasis,  or  the  sleeping  sick- 
ness, is  a  chronic  disorder  marked  by  fever,  wasting, 
and  lethargy.  The  parasites  can  be  found  in  the  blood, 
but  more  often  in  the  cerebrospinal  fluid.  No  way  of 
establishing  an  immunity  is  known. 


CHAPTER  XII. 

DISEASES  CAUSED  BY  UNKNOWN 
MICRO-ORGANISMS 

UNDER  this  head  come  a  number  of  diseases  such 
as  scarlet  fever,  measles,  German  measles,  smallpox, 
and  chicken-pox,  which  are  often  classed  together 
under  the  name  of  exanthemata,  because  they  are  all 
characterized  by  skin  eruptions  and  symptoms  of  gen- 
eral infection. 

SCARLET  FEVER. 

The  infection  almost  always  occurs  from;  direct 
contact;  entering  the  sickroom  may  be  exposure 
enough  to  cause  the  disease.  Objects  which  the  pa- 
tient has  touched  will  transmit  the  infection,  such  as 
linen,  clothing,  furniture,  and  playthings.  Physicians 
and  nurses  sometimes  carry  the  infection,  although 
they  themselves  may  not  be  affected.  Milk  has  been 
known  to>  carry  the  infection  and  cause  serious  epi- 
demics. The  milk  in  such  cases  is  infected  at  the  dairy 
by  someone  who  has  the  disease.  The  infection  may 
be  transmitted  at  any  time  during  the  disease,  but 
especially  during  the  period  of  desquamation. 

In  order  to  prevent  it  from  spreading,  the  sick- 
room in  private  homes  should  be  as  far  away  as  pos- 
sible from  the  room  occupied  by  other  members  of  the 
family.  Admission  to  the  room  should  be  denied  to 
(122) 


DISEASES  FROM  MICRO-ORGANISMS.  123 

everyone  except  the  physician  and  the  nurse.  The 
physician  should  wear  a  gown  and  cap  when  entering 
the  room,  and  should  pass  directly  out  of  the  house 
after  visiting  the  patient.  The  nurse  too  should  wear 
a  gown  over  the  uniform,  and  a  cap  over  the  hair,  both 
being  removed  when  it  is  necessary  to  go  to  other 
parts  of  the  house.  During  the  period  of  desquama- 
tion  skin  should  be  kept  anointed  with  plain  or  car- 
bolized  vaselin,  as  preferred,  in  order  to  keep  the  par- 
ticles of  skin  from  spreading  about.  Quarantine  may 
be  raised  when  the  desquamation  has  completely 
ceased.  Before  the  patient  is  discharged  a  full  bath 
in  weak  bichloride  of  mercury  solution,  i :  10,000, 
should  be  given,  taking  particular  care  to  cleanse  the 
hair.  The  room  and  contents  should  be  disinfected 
after  the  manner  already  described. 

MEASLES. 

Measles  is  a  contagious  and  infectious  disease  that 
generally  occurs  during  childhood,  although  adults 
may  contract  it.  It  spreads  with  great  rapidity  and 
generally  in  epidemics.  The  specific  agent  of  infection 
is  probably  inhaled,  causing  the  first  symptoms  to  ap- 
pear in  the  nose  and  throat. 

The  infectious  material  is  undoubtedly  in  the 
secretions  of  the  nose  and  throat  of  the  sick  patients. 
It  may  be  spread  by  the  attendants  on  the  patient,  by 
furniture,  hangings,  carpets,  by  flies  and  insects.  In 
preventing  the  spreading  of  the  disease  special  atten- 


124  BACTERIOLOGY. 

tion  should  be  given  to  destroying  the  secretions  from 
the  nose  and  throat.  These  should  be  collected  in 
paper  bags  and  burned.  The  patient  should  be  quar- 
antined until  the  skin  and  mucous  membranes  are  clear. 
After  recovery  the  room  should  be  disinfected. 

RUBELLA,  OR  GERMAN  MEASLES. 

The  infection  is  very  much  like  measles,  but  is 
usually  not  so  severe.  In  preventing  its  spread  the 
same  precautions  should  be  taken  as  in  measles. 

VARIOLA,  OR  SMALLPOX. 

Smallpox  is  an  acute  infectious  disease  character- 
ized by  a  skin  eruption  that  passes  successively  through 
the  stages  of  papule,  vesicle,  pustule,  and  crust,  and 
usually  leaves  a  depressed  scar.  The  infectious  agent 
is  in  the  pustules,  secretions,  excretions,  and  in  the 
breath.  The  scales  are  particularly  infectious,  form- 
ing a  part  of  the  dust  in  the  room  and  becoming 
attached  to  the  furniture,  hangings,  and  clothing.  The 
poison  is  very  tenacious  and  remains  virulent  for 
months. 

In  caring  for  smallpox  patients  the  first  thing  to 
do  is  to  isolate  them,  preferably  in  a  building  removed 
from  other  dwellings,  because  of  the  possibility  of  the 
virus  being  carried  in  the  air.  The  strictest  quarantine 
should  be  enforced  not  only  of  the  patients,  but  of  the 
attendants.  Everyone  that  has  been  exposed  to  the 
contagion  should  be  vaccinated  and  kept  under  obser- 


DISEASES  FROM  MICRO-ORGANISMS.  125 

vation  for  sixteen  days.  During  the  illness  the  dis- 
charges from  the  mouth,  nose,  and  intestines  should 
be  disinfected.  The  quarantine  must  be  maintained 
until  the  skin  is  entirely  free  from  crusts  and  scales. 

The  method  and  principles  of  immunization  to 
smallpox  have-  been  described  under  the  subject  of 
immunity. 

CHICKEN-POX,  OR  VARICELLA. 

This  is  an  acute  infectious  disease  of  children.  It 
is  spread  in  the  same  manner  as  smallpox,  but  to  pre- 
vent its  spreading  the  precautions  need  not  be  so 
rigidly  enforced,  because  it  is  not  so>  serious  an  infec- 
tion. The  patient  is  kept  from  contact  with  other 
children,  and  after  recovery  the  room  should  be 
disinfected. 

RABIES,  OR  HYDROPHOBIA. 

Rabies  is  a  disease  common  among  animals,  par- 
ticularly dogs,  although  cats,  cattle,  and  horses  may  be 
infected.  It  is  transmitted  from  one  animal  to  an- 
other, and  to  man  through  the  saliva  from  the  bites  of 
rabid  animals.  The  poison  acts  upon  the  tissue  of  the 
brain  and  spinal  cord,  being  carried  there  along  the 
nerve-trunks.  The  incubation  period  is  from  forty  to 
sixty  days. 

In  animals  the  disease  begins  with  a  stage  of  ex- 
citement and  restlessness,  followed  by  depression,  diffi- 
culty in  swallowing,  and  paralysis.  In  man  there  is 
first  headache  and  depression,  later  difficulty  in  swal- 


126  BACTERIOLOGY. 

lowing,  and  spasm  of  the  muscles  of  respiration.  The 
spasms  are  very  painful  and  may  be  induced  even  by 
the  sight  of  water.  This  is  the  origin  of  the  name 
hydrophobia,  which  means  fear  of  water. 

All  efforts  to  find  the  cause  of  the  infection  in  the 
brain  and  spinal  cord  have  been  fruitless.  Peculiar 
bodies,  called  Negri  bodies,  are  quite  constantly  found 
in  the  brain  and  spinal  cord,  which  many  believe  are 
parasites  belonging  to  the  animal  kingdom,  and  classed 
as  protozoa.  The  diagnosis  of  rabies  can  be  made 
either  by  finding  the  Negri  bodies  or  by  reproducing 
the  disease  in  rabbits  by  inoculating  them  in  the  brain 
with  portions  of  the  spinal  cord  of  rabid  animals, 
immunity  jt  js  due  tQ  the  stucjies  of  Pasteur  that  we  are  able 

to  immunize  against  rabies.  He  found  that  the  virus 
of  rabid  dogs  could  be  intensified  by  inoculating  a 
series  of  rabbits  until  the  inoculation  period  could  be 
shortened  to  six  or  seven  days.  The  spinal  cords  of 
rabbits  inoculated  in  this  way  contain  the  virus  in  its 
most  concentrated  form,  and  is  spoken  of  as  the  fixed 
virus. 

The  fixed  virus  may  be  attenuated  by  drying 
the  spinal  cords  and,  if  human  beings  are  now  inocu- 
lated with  portions  of  the  tissue,  beginning  first  with 
the  most  attenuated  and  then  with  more  and  more 
virulent  tissue,  an  active  immunity  is  established. 
This  is  the  method  now  in  use  in  the  treatment  of  per- 
sons who  have  been  bitten  by  rabid  dogs,  and  it  can 
be  applied  during  the  forty-  to  sixty-  day  incubation 
period.  It  has  proven  very  successful.  In  the  last  ten 


DISEASES  FROM  MICRO-ORGANISMS.  127 

years  50,000  people  have  been  immunized  in  this  way, 
with  failure  in  only  i  per  cent. 

YELLOW  FEVER. 

This  is  an  acute  infectious  disease  the  cause  of 
which  is  not  known,  but  it  has  been  proved  that  the 
infection  may  be  transmitted  by  a  certain  kind  of  mos- 
quito called  the  Stegomyia  fasciata.  The  blood  of 
yellow-fever  patients  contains  the  virus  for  a  period  of 
three  days  during  the  sickness,  and  as  the  stegomyia 
feeds  on  the  blood  of  the  patient  during  this  time,  it 
becomes  infected.  The  mosquito  cannot  transmit  the 
infection  at  once,  not  until  twelve  days  have  elapsed. 
If  it  bites  healthy  people  now,  it  infects  them  and  the 
fever  develops  after  an  incubation  period  of  five  days. 

Yellow  fever  is  primarily  a  disease  of  the  tropical 
climate,  particularly  of  the  Spanish-American  coun- 
tries. It  is  occasionally  imported  to  the  temperate 
climate,  as  numerous  epidemics  in  the  seaport  cities  of 
the  United  States  testify.  To  prevent  the  spread  of 
the  disease  efforts  must  be  directed  to  the  destruction 
of  the  breeding  places  of  the  mosquitoes,  and  to  pre- 
vent them  from  biting  yellow-fever  patients.  The  Preven- 
former  means  a  complete  cleaning  up  and  draining  of 
the  swamps  and  marshes.  All  yellow-fever  patients 
must  be  screened  to  prevent  the  mosquitoes  from  biting 
them..  In  countries  where  the  infection  prevails,  all 
houses  should  be  screened.  Such  measures  as  these 
rendered  the  Panama  Canal  Zone,  formerly  a  hotbed 
of  yellow  fever,  a  safe  place  in  which  to  live. 


128  BACTERIOLOGY. 

ACUTE  ANTERIOR  POLIOMYELITIS. 

This  is  an  acute  infectious  disease  affecting  the 
gray  matter  of  the  spinal  cord,  causing  paralysis  of 
groups  of  muscles.  It  occurs  in  sporadic  and  epidemic 
form.  It  affects  children  particularly,  and  while  the 
mortality  rate  is  low  the  deformities  resulting  from 
the  paralysis  are  very  disfiguring. 

During  the  past  year  Drs.  Flexner  and  Noguchi, 
at  the  Rockefeller  Institute  in  New  York,  have  been 
successful  in  cultivating  an  organism  from  the  spinal 
cords  of  fatal  cases  of  this  disease.  By  inoculating 
monkeys  with  the  cultures  they  have  reproduced  the 
disease  and,  after  the  death  of  the  animals,  have  re- 
covered the  organism  again  from,  the  spinal  cord. 

How  the  infection  is  spread  is  not  known.  It  is 
assumed  that  the  discharges  from  the  nose  and  throat 
are  infectious;  so  they  should  be  collected  and  de- 
stroyed. As  an  added  precaution,  the  patient  should 
be  isolated.  No  method  of  immunization  is  known. 

ACUTE  RHEUMATIC  FEVER. 

This  disease  is  generally  conceded  to  be  infectious, 
but  the  cause  is  as  yet  unknown.  Several  kinds  of 
bacteria,  among  them  the  streptococci  and  staphylo- 
cocci,  have  been  described  as  its  cause.  They  have 
been  cultivated  from  the  joints,  blood,  tonsils,  and 
heart-valves  of  rheumatic-fever  patients.  An  infec- 
tion very  much  like  rheumatic  fever  has  been  produced 
by  inoculating  animals  with  the  cultures.  It  is  not  cer- 


DISEASES  FROM  MICRO-ORGANISMS.  129 

tain,  however,  whether  these  organisms  are  present  as 
the  actual  cause  of  the  disease,  or  are  only  secondary 
invaders. 

MUMPS. 

This  is  an  acute  infectious  disease  affecting-  the 
salivary  glands  in  infants  and  young  adults.  It  is 
contagious,  being  spread  directly  from  one  patient  to 
another.  The  infectious  agent  is  unknown. 

TYPHUS  FEVER. 

While  characteristic  bacilli  have  been  described  in 
the  blood  of  patients  sick  with  this  disease,  efforts  to 
cultivate  them  have  not  been  successful.  The  infection 
can  be  transmitted  to  monkeys  by  injecting  them  with 
the  blood  of  patients.  The  infection  can  be  carried  by 
the  body  louse  (Pedkulus  vestimentorum) , 


CHAPTER  XIII. 

THE  TECHNIQUE  OF  PREPARATIONS  FOR  AND  THE 
COLLECTION  OF  MATERIAL  FOR  BACTERIO- 
LOGICAL EXAMINATION. 

IT  is  not  strictly  a  part  of  the  nurse's  work  to 
collect  specimens  for  bacteriological  examination,  but 
sometimes  the  occasion  arises  when  the  nurse  can 
render  valuable  assistance  by  knowing  how  to  do  these 
things.  On  the  other  hand  the  preparation  of  the 
patient  for  bacteriological  procedures,  such  as  punc- 
tures for  aspirating  fluids  and  the  making  of  cultures 
from  the  circulating  blood,  is  quite  properly  within  the 
duties  of  the  nurse.  The  directions  that  follow  will 
serve  as  a  guide,  but  may  need  to  be  modified  or 
changed  according  to  the  ideas  of  the  physician  in 
attendance. 

THE  COLLECTION  OF  URINE. 

TiectiCo°n"  A  sterile  test-tube  plugged  with  cotton  is  used  to 

°fmens1"  collect  the  urine,  and  the  urine  must  be  obtained  by 
catheter.  The  usual  technique  is  followed  in  preparing 
the  patient,  the  catheter  introduced,  and  the  first  part 
of  the  urine  allowed  to  escape.  The  cotton  plug  is 
now  twisted  out  of  the  tube,  the  mouth  of  the  tube 
passed  through  the  flame  of  an  alcohol  lamp,  and  the 
urine  allowed  to  fill  the  tube  one<-half  or  three-fourths 
full.  The  stopper  is  then  replaced  and  the  tube  kept 
in  the  upright  position. 
(130) 


TECHNIQUE.  131 

SPUTUM. 

Specimens  to  be  examined  for  tubercle  bacilli 
should  be  collected  in  a  clean,  wide-mouthed  bottle  that 
can  be  tightly  corked  to  prevent  leakage.  Sputum  to 
be  examined  for  other  kinds  of  bacteria  should  be  col- 
lected in  a  bottle  plugged  with  cotton  and  previously 
sterilized.  If  the  outside  of  the  bottle  has  been  soiled 
with  the  sputum,  it  should  be  washed  off  with  a  5  per 
cent,  solution  of  carbolic  acid. 

FECES. 

The  stool  may  be  passed  directly  into  a  sterile 
fruit- jar  or  into  a  sterile  bed-pan,  and  then  transferred 
to  the  jar.  The  specimen  may  be  transferred  either  by 
pouring  or  by  means  of  sterile  forceps  or  a  wooden 
spatula. 

BLOOD  FOR  WIDAL  REACTION. 

The  blood  is  obtained  best  by  pricking  the  lobe  of 
the  ear  with  a  needle  having  a  cutting  edge.  The  skin 
should  be  cleansed  with  alcohol,  and  the  needle  must 
be  sterile.  The  best  way  to  collect  the  blood  is  in  a 
capillary  glass  tube  by  placing  one  end  of  the  tube  in 
the  drop  of  blood  and  lowering  the  other  end  enough 
to  allow  the  blood  to  flow  in  easily  until  the  tube  is 
one-half  full.  If  a  capillary  tube  is  not  at  hand,  the 
blood  may  be  collected  on  a  glass  slide  or  on  glazed 
paper  like  a  calling  card.  Two  or  three  drops  are 
enough. 


132  BACTERIOLOGY. 

THROAT  CULTURES. 

Outfits  for  making  throat  cultures  are  supplied 
by  the  Bureau  of  Health  in  most  cities,  and  consist  of 
a  sterile  swab  in  a  test-tube  and  a  tube  of  culture 
medium.  The  patient  is  placed  in  a  good  light,  the 
tongue  held  down  by  a  tongue-depressor  or  spoon- 
handle,  and  the  swab  rubbed  over  the  inflamed  part 
of  the  throat.  The  material  on  the  swab  is  then 
rubbed  directly  over  the  surface  of  the  culture  medium. 
After  use  the  swab  may  be  burned  or  replaced  in  the 
tube  and  sent  with  the  culture. 

Pus. 

When  the  amount  of  the  pus  is  sufficient,  it  may 
be  collected  directly  into  a  sterile  test-tube.  If  cultures 
are  made,  the  swab  and  culture  tube  of  a  throat-cul- 
ture outfit  may  be  used.  The  pus  is  collected  on  the 
swab  and  then  rubbed  over  the  culture  medium,  just 
as  in  making  a  throat  culture. 

MILK  AND  WATER. 

Specimens  should  be  collected  in  glass-stoppered 
bottles,  of  4-  or  6-  ounce  capacity,  which  are  sterile. 
Specimens  of  milk  should  be  well  mixed  before  the 
sample  is  taken.  Specimens  of  both  milk  and  water 
must  be  kept  cold  and,  if  it  is  necessary  to  send  them 
any  distance,  they  must  be  packed  in  ice. 

All  kinds  of  specimens   should  be  labeled   with 


The 
tech- 


TECHNIQUE.  133 

the  names  of  the  patient  and  the  physician,  the  date, 
and  the  character  of  the  examination  required. 

ASPIRATION  OF  CHEST,  BLOOD-CULTURES. 

The  preparation  of  the  patient  for  the  aspiration 
of  fluid  from  the  body  cavities,  for  lumbar  puncture, 
and  cultures  from  the  blood  must  be  performed  with  prtei?Ssa" 
the  greatest  care,  to  insure  the  patient  against  infection 
and  to  prevent  the  contamination  of  the  specimen  with 
other  bacteria,  particularly  those  in  the  skin. 

For  aspirations  of  the  chest  or  joints  and  for  lunv 
bar  puncture  the  skin  should  be  cleansed  with  benzene 
and  then  tincture  of  iodine  applied.  For  taking  cul- 
tures from  the  blood  this  method  is  not  suitable, 
because  the  tincture  of  iodine  discolors  the  skin  so 
much  that  the  veins  cannot  be  seen  clearly.  The  veins 
usually  selected  are  at  the  bend  of  the  elbow.  The 
skin  is  first  washed  thoroughly  with  green  soap  and 
water,  then  with  alcohol  and  ether.  A  wet  bichloride 
of  mercury  towel  is  placed  over  the  skin  and  allowed 
to  remain  for  one  hour.  Before  the  culture  is  taken 
the  skin  is  again  washed  with  ether.  A  bandage  is 
applied  somewhat  above  the  elbow,  and  tight  enough 
to  cause  the  veins  to  stand  out  so  that  they  can  be  more 
readily  punctured.  The  blood  is  drawn  into  a  sterile 
glass  syringe  that  has  been  sterilized  by  boiling  in  a 
covered  receptacle,  which  can  be  brought  to  the  bed- 
side unopened. 


GLOSSARY. 


Abrasion.    A  spot  rubbed  bare  of  skin  or  mucous  membrane. 

Accessory  sinuses.  Cavities  in  the  bones  of  the  skull,  some 
containing  blood  and  some  air. 

Aerobic.    Requiring  air  or  free  oxygen  for  growth. 

Anaerobic.  Able  to  live  only  in  the  absence  of  air  or  free 
oxygen. 

Anemia.  A  condition  in  which  the  blood  is  lacking  either  in 
quantity  or  quality. 

Aniline  dyes.  Colors  derived  by  chemical  process  from  coal- 
tar. 

Animalcules.    Very  small  animal  organisms. 

Antitoxin.  A  proteid  substance  developed  in  the  bodies  of 
man  or  animals  that  has  the  power  of  neutralizing 
poisons. 

Arthritis.    Inflammation  of  a  joint. 

Bacillus  (pi.  bacilli).     A  rod-shaped  organism  belonging  to 

the  vegetable  kingdom. 

Bactericidal.    Possessing  the  power  of  destroying  bacteria. 
Bacterins.     Killed  bacteria   suspended   in   fluid   and   injected 

under  the  skin  in  the  treatment  of  some  diseases.     Also 

called  vaccines. 

Bacteriology.    The  study  of  bacteria. 
Bacteriolysins.     Substances  developed  in  the  body  which  are 

capable  of  dissolving  bacteria. 
Bacterium  (pi.  bacteria).     A  unicellular  organism  belonging 

to  the  vegetable  kingdom. 
Binary  fission.     The  method  of  multiplication  of  bacteria  in 

which  the  organism  splits  in  half. 

Carbohydrates.  A  compound  composed  of  carbon,  hydrogen, 
and  oxygen. 

(135) 


136  GLOSSARY. 

Carrier.  A  person,  not  sick  with  any  disease,  who  carries  dis- 
ease-producing organisms  in  the  body  and  is  capable  of 
infecting  others  with  them. 

Cell.    The  smallest  unit  of  structure  in  plant  and  animal  life. 

Chancre.  The  primary  sore  at  the  point  of  infection  in 
syphilis. 

Cellulitis.    An  inflammation  in  the  soft  tissues  of  the  body. 

Coccus.    A  bacterium  having  a  spherical  shape. 

Colony.  A  mass  of  micro-organisms  of  the  same  kind  that 
has  developed  from  one  organism. 

Contagion.  The  transmission  of  disease  by  mediate  or  im- 
mediate contact. 

Culture.  A  mass  of  micro-organisms  growing  on  laboratory 
culture  media. 

Cystitis.    Inflammation  of  the  urinary  bladder. 

Deodorant.    A  substance  that  destroys  objectionable  odors. 
Disinfectant.     A  physical   or  chemical   agent  that  destroys 
bacteria. 

Empyema.    A  collection  of  pus  in  the  pleural  cavity. 

Endocarditis.    An  inflammation  of  the  lining  of  the  heart. 

Endotoxin.  A  poison  retained  in  the  body  of  a  bacterium  and 
set  free  when  the  bacterium  disintegrates. 

Enzyme.  An  unorganized  ferment  formed  in  the  bodies  of 
plants  and  animals  capable  of  splitting  complex  sub- 
stances into  simpler  forms  without  being  changed  itself. 

Erysipelas.    An  acute  spreading  infection  in  the  skin. 

Etiology.  The  study  of  the  causes  of  disease  and  the  way 
disease  is  transmitted. 

Fermentation.     The    decomposition    of    complex    substances 

into  simpler  forms  by  the  action  of  a  ferment. 
Flagellum  (pi.  flagella).    A  whip-like  process  extending  from 

the   body   of   a   bacterium   which   propels    the   organism 

about. 
Filtration.     The  passage  of  fluid  through  a  filter  to  remove 

the  solid  particles. 


GLOSSARY.  137 

Hemoglobin.  The  coloring  matter  contained  in  the  red 
blood-corpuscles  which  gives  the  blood  its  red  color. 

Immunity.    The  resistance  of  the  body  to  disease. 

Incubation.  The  period  between  the  entrance  of  disease-pro- 
ducing bacteria  into  the  body  and  the  signs  and  symptoms 
of  disease. 

Infection.  The  entrance  into  the  body  of  bacteria  resulting 
in  injury  or  disease. 

Inhibition.    The  arrest  or  restraint  of  bacterial  growth. 

Inoculate.  To  put  infectious  material  into  the  body  to  pro- 
duce disease  or  into  culture  media  to  produce  bacterial 
growth. 

Larva  (pi.  larvae).    The  stage  of  insect  development  after  it 

leaves  the  egg  in  which  it  resembles  a  worm. 
Lesion.    An  abnormal  condition  of  any  tissue  or  organ  due 

to  injury  or  disease. 

Leucocyte.    The  white  blood-corpuscle  of  the  blood. 
Luetin  reaction.    A  skin  test  for  the  detection  of  syphilis. 
Lumbar  puncture.     The   introduction   of   a   needle   into   the 

space   around   the   spinal   cord   for   the   removal   of   the 

cerebrospinal  fluid. 

Medium  (pi.  media).    The  material  used  for  the  cultivation 

of  bacteria. 
Meningitis.    An  inflammation  of  the  membranes  covering  the 

brain  and  spinal  cord. 

Morphology.    The  study  of  the  form  and  structure  of  bacteria. 
Mycelium.    The  thread-like  processes  of  fungi. 

Necrosis.    The  death  of  tissue. 

Negri  bodies.     Minute  bodies  found  in  the  brain  of  persons 

and  animals  infected  with  rabies. 
Nucleus  (pi.  nuclei).    The  spherical  body  found  in  cells  which 

controls  its  life  and  activity. 

Opsonin.  A  substance  in  the  blood-serum  which  makes  bac- 
teria more  easily  absorbed  by  the  leucocytes. 


138  GLOSSARY. 

Orchitis.    An  inflammation  of  the  testicle. 

Organic.  Relating  to  substances  derived  from  living  or- 
ganisms. 

Osteomyelitis.  An  inflammation  of  the  medullary  cavity  of 
bone. 

Otitis  media.    An  inflammation  of  the  middle  ear. 

Papule.    A  small,  solid  elevation  of  the  skin. 

Parasite.  A  plant  or  animal  that  lives  on  or  in  another  living 
organism. 

Pasteurization,    The  arrest  of  bacterial  growth  by  heat. 

Pathogenic.    Disease-producing. 

Phagocyte.  The  white  blood-corpuscle  of  the  blood  that  en- 
velops and  destroys  bacteria. 

Pericarditis.    An  inflammation  of  the  covering  of  the  heart. 

Pseudopod.  A  transient  protrusion  of  the  protoplasm  of  an 
ameba. 

Protozoon  (pi.  protozoa).    A  unicellular  animal  organism. 

Prophylaxis.    The  prevention  of  disease. 

Pyogenic.    Pus-producing. 

Puerperal  fever.  An  infection  starting  in  the  uterus  after 
childbirth. 

Pustule.    A  small  elevation  of  the  skin  containing  pus. 

Quarantine.  Isolation  on  account  of  suspected  contagious 
disease. 

Saprophyte.    An  organism  capable  of  living  on  dead  matter. 

Septicemia.  The  condition  resulting  from  the  invasion  of  the 
body  by  bacteria  and  the  absorption  of  the  poisons  pro- 
duced by  them. 

Spirochete.    A  spiral  or  corkscrew-shaped  organism. 

Sterile.    Free  from  micro-organisms. 

Suppuration.    The  formation  of  pus. 

Tenesmus.    Ineffectual  straining  at  stool. 
Tuberculin.     A  preparation  made  from  tubercle  bacilli  and 
containing  their  toxins. 


GLOSSARY.  139 

Vaccine.    See  bacterin. 

Vesicle.    A  small  elevation  of  the  skin  containing  serum. 

Vacuole.    A  cavity  in  the  protoplasm  of  a  cell. 

Virus.    An  animal  poison  capable  of  producing  disease. 

Widal  reaction.     A  blood-test  for  the  detection  of  typhoid 

fever. 
Wassermann    reaction.      A    blood-test    for    the    detection    of 

syphilis. 


INDEX. 


Achorion  Schonleini,  103 

Actinomycosis,  99 

Acute     anterior     poliomyelitis, 

128 

Acute  rheumatic  fever,  128 
Agglutinins,  40 
Air,  bacteria  in,  13 
Amebic  dysentery,  111 

diagnosis  of,  112 

path  of  infection,  112 
Ameba  histolytica,  111 

morphology,  112 
Anaphylaxis,  40 
Anthrax,  78 
bacillus,  79 
Antibody,  40 

Antimeningitis  serum,  53 
Antisepsis,  17 
Antitoxin,  unit  of,  39 
Apartments,  disinfection  of,  28 
Asiatic  cholera,  84 

carriers,  84 

distribution  of,  83 

immunity,  85 

path  of  infection,  84 

prevention,  84 

Aspiration,  preparation  for,  133 
Attenuation,  31 
Autoclave,  20 

Bacillus,  anthrax,  78 
Bordet  and  Gengou,  75 
coli  communis,  55 
diphtheria}  86 
Ducrey,  76 
dysentery,  65 


Bacillus,  Koch-Weeks,  76 
lactis  aerogenes,  68 
leprosy,  96 
mallei,  72 

mucosus  capsulatus,  67 
paracolon,  56 
paratyphoid,  56,  64 
pestis,  80 

proteus  vulgaris,  68 
pyocyaneus,  82 
rhinoscleroma,  69 
smegma,  92 
tetanus,  70 
tubercle,  91 
typhoid,  56 
Bacteria,  aerobic,  11 
anaerobic,  11 
classification  of,  6 
commercial  use  of,  15 
cultivation  of,  12 
definition  of,  6 
distribution  of,  13 
effect  of  drying  on,  17 

of  heat  on,  18 

of  sunlight  on,  18 
fermentation  by,  10 
function  of,  14 
influence  of  acid  on,  12 

of  alkali  on,  12 
'of  moisture  on,  12 

of  temperature  on,  12 
injury  caused  by,  34 
light  produced  by,  10 
morphology  of,  8 
motility  of,  10 
nutriment  of,  11 

(141) 


142 


INDEX. 


Bacteria,  odors  produced  by,  10 
pigments  produced  by,  10 
reproduction  of,  9 
size  of,  8 
structure  of,  6 
Bichloride  of  mercury,  23 
Blastomyces,   101 
Blood,  collection  of,  131 

cultures  of,  133 
Bubonic  plague,  80 
bacillus  of,  80 
immunity  to,  82 
prevention  of,  81 
spread  of,  81 

Cellulitis,  43 

Chicken-pox,  125 

Coccus,  8 

Contagion,  29 

Clothing,  disinfection  of,  26 

Culture  media,  12 

Diphtheria,  85 

antitoxin,  preparation  of,  38 
serum  sickness,  90 
treatment,  90 
bacillus,  85 

morphology,  86 
carriers,  89 
diagnosis  of,  87 
disinfection  after,  90 
spread  of,  88 
toxin,  87 
Diplococcus,  8 

of  pneumonia,  48 
Disinfectant   solutions,   22,   23, 

24 

gases,  25 
Disinfection,  17 


Empyema,  44 

Endocarditis,  43,  44,  47,  75 
Endotoxins,  35 

Farcy,  73 

Favus,  parasite  of,  103 

Feces,  collection  of,  131 

disinfection  of,  26 
Flagellum,  10 
Food,  bacteria  in,  14 
Formaldehyde  gas,  25,  27 
Formalin,  22 

German  measles,  124 
Germs,  discovery  of,  1 

as  cause  of  disease,  3 
Glanders,  72 

bacillus,  72 
toxins  of,  73 

diagnosis  of,  74 
Gonococcus,  45 
Gonorrhea,  45 
Gonorrheal  conjunctivitis,  47 

vaginitis,  47 

Hydrophobia,  125 

Immunity,  35 

acquired,  36 

natural,  35 

passive,  38 

racial,  35 

vaccines  in,  37 
Infection,  definition  of,  29 

how  it  takes  place,  32 

injury  as  cause  of,  32 
Infestation,  30 
Influenza  bacillus,  51,  74 


INDEX. 


143 


Leprosy,  bacillus  of,  96 

prevention  of,  98 
Liver  abscess,  ameba  in,  111 

B.  pyocyaneus  in,  82 
Luetin  reaction,  116 
Lumbar  puncture,  51,  133 

Malarial  fever,  118 
parasite  of,  118 
prevention  of,  119 

Mallein,  74 

Malta    fever,    micrococcus    of, 
77 

Measles,  123 

Meningitis,  47,  SO 
precautions,  52 
serum,  53 

Meningococcus,  51 
carriers,  52 

Mercury,  bichloride  of,  22 

Micrococcus    melitensis,    77 
tetragenus,  44 

Microsporon  furfur,  103 

Miliary  tuberculosis,  94 

Milk,  bacteria  in,  105 
collection  of,  132 
contamination  of,  105 
diseases  spread  by,  107 
pasteurization  of,  105 

Molds,  102 

Mumps,  129 

Negri  bodies,  126 

Oi'dium  albicans,  103 
Ophthalmia,  neonatorum,  47 
Opsonins,  40 
Osteomyelitis,  44 


Parasite,  definition  of,  29 
Paratyphoid  fever,  56,  64 
Pasteurization,  105 
Pericarditis,  82 
Phagocytosis,  39 
Pigments,  bacterial,  10 
Pityriasis  versicolor,  103 
Pneumococcus,  48 
Pneumonia,  44 

precautions,  50 
Poliomyelitis,    acute    anterior, 

128 

Protozoa,  111 
Ptomaines,  16,  29 
Puerperal  fever,  43,  44 
Pus,  collection  of,  132 
Pyemia,  34,  43 
Pyocyanase,  83 
Pyogenic  cocci,  group  of,  42 

Rabies,  125 

immunization  against,  126 
Relapsing  fever,  spirochete  of, 

116 

Rheumatic  fever,  acute,  128 
Ringworm,  parasites  of,  104 
Rubella,  124 

Saprophyte,  29 
Scarlet  fever,  122 
Septicemia,  34,  43,  82 
Sleeping  sickness,  organism  of, 

120 

Smallpox,  124 
Smegma  bacillus,  92 
Soil,  bacteria  in,  13 
Spirillum,  8 

of  Asiatic  cholera,  83 

Vincent's,  117 


144 


INDEX. 


Spontaneous  generation,   1 

Spores,  9 

Sputum,  collection  of,  131 

disinfection  of,  26 
Staphylococcus  epidermidis  al- 
bus,  42 

pyogenes  albus,  42 
aureus,  42 
citreus,  42 
Sterilization,  17 

by1  boiling,  19 

by  dry  heat,  18 

by  steam,  19 

by  steam  under  pressure,  20 

fractional,  20 

Streptococcus  pyogenes,  44 
Syphilis,  113 

diagnosis  of,  116 

manifestations  of,  115 

path  of  infection  in,  114 

Tetanus  antitoxin,  72 

bacillus,  70 

path  of  infection,  71 

toxin,  72 

Throat  culture,  method  of  tak- 
ing, 132 

Thrush,  fungus  of,  103 
Tinea,  circinata,  104 

sycosis,  104 

tonsurans,  104 

trichophyton,  104 
Toxemia,  34 
Toxins,  35 

Treponema  pallidum,  113 
Trypanosomes,  120 
Tubercle  bacillus,  in  exudates, 

93 
in  urine,  92 


Tubercle  bacillus,  lesions  caused 

by,  94 

morphology  of,  91 
paths  of  infection,  93 
staining  of,  92 
toxins  of,  94 
Tuberculin  reaction,  95 

treatment,  96 
Tuberculosis,  91 
Typhoid  bacillus,  56 
in  milk,  59 
in  water,  58 
carriers,  60 

fever,  immunity  to,  61,  62 
path  of  infection,  58 
prevention  of,  60 
Typhus  fever,  129 

Urine,  collection  of,  130 
disinfection  of,  26 
tubercle  bacillus  in,  92 

Varicella,  125 
Variola,  124 
Vincent's  angina,  117 
Virulence,  31 

Wassermann  reaction,  116 
Water,  bacteria  in,  13,  107 

collection  of,  132 

filtration  of,  109 

purification  of,  108 

sewage      contamination      of, 
109 

typhoid  bacillus  in,  58 
Whooping-cough,  75 
Widal  reaction,  62 

Yeasts,  100 
Yellow  fever,  127 


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Anatomy. 

\V7HILE  many  a  physician  has  been  handicapped  by  an  im- 
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Hand-Book  of  Anatomy 


Being  a  Complete  Manual  of 
Anatomy,  Including  the  Anatomy 
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By  James  K.  Young,  M.D. 

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complete  in  the  gen- 
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PHYSIOLOGY 

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WHILE  American  surgery  is  the  admiration  of  the  world,  the 
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tific accuracy  has  been 
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nold Lorand,  the  au- 
thor of  "Old  Age 


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of  Diet. 


By  Dr.  Arnold  Lorand, 

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Deferred."  •  Dr.  Lor- 
and's  qualifications 
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been  guaranteed  in  ad- 
vance. The  book  has 
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American  Medical  As- 
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Translated     from     the     Original 
German  Edition  with  an  Intro- 
duction by  Victor  C.  Vaughan, 
M.D.,  Ann  Arbor,  Mich. 
Being  a  complete  code  of  instruc- 
tions as  to  the  different  foods  and 
how     they     can     be     best     em- 
ployed. 

Royal  Octavo,  425  pages. 

Handsomely  Bound  in  Cloth 
(uniform  with  "Old  Age  De- 
ferred"), $2.50,  net. 


Other  Publications   of  F.  A.    Davis  Company,  Philadelphia 


Infantile  Paralysis. 


HEARSAYevidence  is  no  evidence;  therefore,  a  large  number 
of  physicians  who  have  had  little  or  no  experience  with 
cases  of  acute  poliomyelitis,  could  not  in  the  nature  of  things 
have  much  to  fall  back  on  when  the  sudden  emergency  arises. 

Frauenthal  and 
Manning  have  sup- 
plied a  textbook  which 
admirably  serves  as 
a  moral  support  when 
the  unexpected  hap- 
pens, or  when,  having 
happened,  the  pros- 


A  Manual  of 

Infantile  Paralysis 

With  Modern  Methods  of 

Treatment 


Including  Reports  Based  on  the 


Treatment    o 
Cases. 


po 


Three    Thousand 


BY 


Henry  W.  Frauenthal,  A.C.,  M.D., 

Surgeon  and  Physlcian-ln-chief  to  the  New  York 

Hospital  for  Deformities  and  Joint 

Diseases,  and 

Jacolyn  Van  Vliet  Manning,  M.D., 

Epidemologist,  Epidemic  of  Acute  Poliomyelitis. 
Wisconsin,  1908. 


pect  of  a  long,  dis- 
couraging siege  with 
the  unfortunate  pa- 
tient looms  up  before 
the  family  doctor. 
This  work  represents 
experience  and  more 
and  more  experience. 
It  tells  what  is  to  be 
done  immediately 
when  the  case  is  sus- 
pected, and  what  shall 
be  done  leisurely 
when  the  acute  stage 
is  past.  There  is  al- 
ways a  best  way  to 
do  things. 

This  work  supplies  much  valuable  aid  in  quick  diagnosis,  out- 
lines the  early  medical  treatment,  and  gives  in  detail  the  best 
approved  restorative  methods,  including  muscle  training.  Sent 
on  approval.  See  order  card. 


Copiously  Illustrated  with  128 
Half-tone  Engravings  (includ- 
ing 12  full-page  plates),  nearly 
all  original. 

Octavo,  374  pages. 
Extra  Cloth,  $3.00,  net. 


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